Unreliable 4G (LTE) connectivity

[Lliure]

Continuing the discussion from Librem 5 Turbo Ultra Version:

@Ick

Did you try to use “4G preferred” (settings)?

Yes, that’s the default setting. Most of the time, the status icon in the upper left corner says either 2G, 4G-with-exclamation-mark, or nothing at all (empty bars). 4G works only 10% of the time.

In other words: whenever I want 4G connectivity, I have to either power cycle the modem kill switch 10 times to make it work, or alternatively, toggle the “Mobile Data” control in Settings off and on 10 times.

It then usually keeps working until I move to a different area. After that, the kill switch dance begins all over.

I have even bought a replacement modem just to check if the modem might be the culprit, but that didn’t help.

To rule out the possibility that the issue might be with my provider, Deutsche Telekom, I have ordered a secondary SIM card and put it in a mobile LTE/5G Wi-Fi router. That secondary way always works.

I’ve been offline like this for twelve months.
4G used to work much better before, but it got worse at one point.
Like, when I got the phone new, I remember it used to show either 4G or 4G-with-exclamation-mark. The latter happened mostly after I switched cells. In that case, I just had to power cycle the modem up to three times to get 4G working.

Today, it’s mostly 2G or 4G-with-exclamation-mark, and I have to power cycle the modem 10 times.

What are good ways to troubleshoot this further?

[irvinewade]

The exclamation mark, I believe, means that you or someone else has turned off data. If roaming is part of your provider’s offering then that could play a part.

[JR-Fi]

There are other reports that Deutche Telekom’s Volte and L5 aren’t compatible, see: Incoming calls in Germany - O2 -> no with vodafone -> YES - #2 by jonsger and VoLTE support progress - #447 by st.boom

This seems to happen around the world. Just need to test others (and other users can give hints here what works or not).

[Edit to add: I don’t think this has ever been explored further as the workaround (changing provider) has been easier, but I wonder if it’s connected to what was shown in IPV6 only hotspot and IPv6…? If you want to start troubleshooting from somewhere. Or it may be that operators just aren’t allowing specific types of modems to their networks.]

[Lliure]

@irvinewade

The exclamation mark, I believe, means that you or someone else has turned off data.

That was my first thought, too. However, I’m not sure how that would explain why power cycling 10 times makes it work. Also, the secondary SIM card (from the same contract) works fine in the 5G router.

@irvinewade

If roaming is part of your provider’s offering then that could play a part.

I’m pretty sure that they do offer it. I don’t use roaming; right now, my focus is on getting it working in my area again, e.g. at home, at the office, and while running errands.

@JR-Fi

There are other reports that Deutche Telekom’s Volte and L5 aren’t compatible

Voice calls usually work fine on either 2G or 4G, but not on 4G-with-exclamation-mark. I don’t know why I would need or want VoLTE.
It’s the Internet connectivity that concerns me most. I want to be able to look things up on the web, read my email, and see entries in my calendar app when I’m on the go.
The articles you’ve linked to seem to be specifically concerned with voice calls.

@JR-Fi

Or it may be that operators just aren’t allowing specific types of modems to their networks.

If that were the case, then how come it sometimes works?
I’d expect it to not work at all.
For example, I’m at home right now, and the L5 has had 4G with zero issues for the last hour. But one minute ago, it suddenly switched to 4G-with-exclamation-mark.

Update: here’s the output of journalctl --facility=daemon --facility=kern the moment the issue occurs:

What the system journal said at 12:22, right as the status changed from 4G to 4G-with-exclamation-mark

Feb 27 12:22:13 ercolano ModemManager[821]: <warn>  [modem0] network reject indication received
Feb 27 12:22:13 ercolano ModemManager[821]: <warn>  [modem0]   service domain: ps
Feb 27 12:22:13 ercolano ModemManager[821]: <warn>  [modem0]   radio interface: lte
Feb 27 12:22:13 ercolano ModemManager[821]: <warn>  [modem0]   reject cause: ue-identity-not-derived-by-network
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0/bearer3] verbose call end reason (3,1008): [cm] ms-identity-not-derived-by-the-network
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0] state changed (connected -> registered)
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0/bearer3] connection #4 finished: duration 1098s, tx: 118305 bytes, rx: 203258 bytes
Feb 27 12:22:13 ercolano NetworkManager[700]: <info>  [1740655333.6437] modem["cdc-wdm0"]: modem state changed, 'connected' --> 'registered' (reason: user-requested)
Feb 27 12:22:13 ercolano dbus-daemon[698]: [system] Activating via systemd: service name='org.freedesktop.nm_dispatcher' unit='dbus-org.freedesktop.nm-dispatcher.service' requested by ':1.10' (uid=0 pid=700 comm="/usr/sbin/NetworkManager --no-daemon ")
Feb 27 12:22:13 ercolano NetworkManager[700]: <info>  [1740655333.6439] device (cdc-wdm0): state change: activated -> failed (reason 'modem-no-carrier', sys-iface-state: 'managed')
Feb 27 12:22:13 ercolano dbus-daemon[698]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
Feb 27 12:22:13 ercolano NetworkManager[700]: <warn>  [1740655333.6592] device (cdc-wdm0): Activation: failed for connection 'Prepaid Contracts'
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0] simple connect started...
Feb 27 12:22:13 ercolano NetworkManager[700]: <info>  [1740655333.6657] device (cdc-wdm0): state change: failed -> disconnected (reason 'none', sys-iface-state: 'managed')
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0] simple connect state (4/8): wait to get fully enabled
Feb 27 12:22:13 ercolano NetworkManager[700]: <info>  [1740655333.7115] policy: auto-activating connection 'Prepaid Contracts' (adcf9c04-57f3-4bca-b30f-b13877182103)
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0] simple connect state (5/8): register
Feb 27 12:22:13 ercolano NetworkManager[700]: <info>  [1740655333.7205] device (cdc-wdm0): Activation: starting connection 'Prepaid Contracts' (adcf9c04-57f3-4bca-b30f-b13877182103)
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0] simple connect state (6/8): bearer
Feb 27 12:22:13 ercolano NetworkManager[700]: <info>  [1740655333.7211] device (cdc-wdm0): state change: disconnected -> prepare (reason 'none', sys-iface-state: 'managed')
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0] simple connect state (7/8): connect
Feb 27 12:22:13 ercolano NetworkManager[700]: <info>  [1740655333.7251] device (cdc-wdm0): state change: prepare -> need-auth (reason 'none', sys-iface-state: 'managed')
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0] state changed (registered -> connecting)
Feb 27 12:22:13 ercolano systemd[1]: Starting Network Manager Script Dispatcher Service...
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0/bearer1] couldn't start network: QMI protocol error (14): 'CallFailed'
Feb 27 12:22:13 ercolano NetworkManager[700]: <info>  [1740655333.8739] device (cdc-wdm0): state change: need-auth -> prepare (reason 'none', sys-iface-state: 'managed')
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0/bearer1] verbose call end reason (3,2001): [cm] no-service
Feb 27 12:22:13 ercolano systemd[1]: Started Network Manager Script Dispatcher Service.
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0/bearer1] couldn't start network: QMI protocol error (14): 'CallFailed'
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0/bearer1] verbose call end reason (3,2001): [cm] no-service
Feb 27 12:22:13 ercolano ModemManager[821]: <warn>  [modem0/bearer1] connection attempt #6 failed: Call failed: cm error: no-service
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0] state changed (connecting -> registered)
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0/bearer1] connection #6 finished: duration 0s, tx: 0 bytes, rx: 0 bytes
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0] simple connect started...
Feb 27 12:22:13 ercolano NetworkManager[700]: <info>  [1740655333.9207] modem["cdc-wdm0"]: modem state changed, 'registered' --> 'connecting' (reason: user-requested)
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0] simple connect state (4/8): wait to get fully enabled
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0] simple connect state (5/8): register
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0] simple connect state (6/8): bearer
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0] simple connect state (7/8): connect
Feb 27 12:22:13 ercolano ModemManager[821]: <info>  [modem0] state changed (registered -> connecting)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer2] couldn't start network: QMI protocol error (14): 'CallFailed'
Feb 27 12:22:13 ercolano NetworkManager[700]: <info>  [1740655333.9739] modem["cdc-wdm0"]: modem state changed, 'connecting' --> 'registered' (reason: user-requested)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer2] verbose call end reason (3,2001): [cm] no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <warn>  [modem0/bearer2] connection attempt #5 failed: Call failed: cm error: no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] state changed (connecting -> registered)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer2] connection #5 finished: duration 0s, tx: 0 bytes, rx: 0 bytes
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect started...
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (4/8): wait to get fully enabled
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.0004] modem["cdc-wdm0"]: modem state changed, 'registered' --> 'connecting' (reason: user-requested)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (5/8): register
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (6/8): bearer
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (7/8): connect
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] state changed (registered -> connecting)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer3] couldn't start network: QMI protocol error (14): 'CallFailed'
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer3] verbose call end reason (3,2001): [cm] no-service
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.0224] modem["cdc-wdm0"]: modem state changed, 'connecting' --> 'registered' (reason: user-requested)
Feb 27 12:22:14 ercolano ModemManager[821]: <warn>  [modem0/bearer3] connection attempt #5 failed: Call failed: cm error: no-service
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.0455] modem["cdc-wdm0"]: modem state changed, 'registered' --> 'connecting' (reason: user-requested)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] state changed (connecting -> registered)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer3] connection #5 finished: duration 0s, tx: 0 bytes, rx: 0 bytes
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect started...
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (4/8): wait to get fully enabled
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (5/8): register
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (6/8): bearer
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.0664] modem["cdc-wdm0"]: modem state changed, 'connecting' --> 'registered' (reason: user-requested)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (7/8): connect
Feb 27 12:22:14 ercolano NetworkManager[700]: <warn>  [1740655334.0666] modem-broadband[cdc-wdm0]: failed to connect modem: Call failed: cm error: no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] state changed (registered -> connecting)
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.0667] device (cdc-wdm0): state change: prepare -> failed (reason 'unknown', sys-iface-state: 'managed')
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer1] couldn't start network: QMI protocol error (14): 'CallFailed'
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer1] verbose call end reason (3,2001): [cm] no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer1] couldn't start network: QMI protocol error (14): 'CallFailed'
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer1] verbose call end reason (3,2001): [cm] no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <warn>  [modem0/bearer1] connection attempt #7 failed: Call failed: cm error: no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] state changed (connecting -> registered)
Feb 27 12:22:14 ercolano NetworkManager[700]: <warn>  [1740655334.0763] device (cdc-wdm0): Activation: failed for connection 'Prepaid Contracts'
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer1] connection #7 finished: duration 0s, tx: 0 bytes, rx: 0 bytes
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.0785] device (cdc-wdm0): state change: failed -> disconnected (reason 'none', sys-iface-state: 'managed')
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect started...
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.0864] policy: auto-activating connection 'Prepaid Contracts' (adcf9c04-57f3-4bca-b30f-b13877182103)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (4/8): wait to get fully enabled
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.0888] device (cdc-wdm0): Activation: starting connection 'Prepaid Contracts' (adcf9c04-57f3-4bca-b30f-b13877182103)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (5/8): register
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.0894] device (cdc-wdm0): state change: disconnected -> prepare (reason 'none', sys-iface-state: 'managed')
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (6/8): bearer
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.0937] device (cdc-wdm0): state change: prepare -> need-auth (reason 'none', sys-iface-state: 'managed')
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (7/8): connect
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.1005] device (cdc-wdm0): state change: need-auth -> prepare (reason 'none', sys-iface-state: 'managed')
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] state changed (registered -> connecting)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer2] couldn't start network: QMI protocol error (14): 'CallFailed'
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer2] verbose call end reason (3,2001): [cm] no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <warn>  [modem0/bearer2] connection attempt #6 failed: Call failed: cm error: no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] state changed (connecting -> registered)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer2] connection #6 finished: duration 0s, tx: 0 bytes, rx: 0 bytes
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.2092] modem["cdc-wdm0"]: modem state changed, 'registered' --> 'connecting' (reason: user-requested)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect started...
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.2512] modem["cdc-wdm0"]: modem state changed, 'connecting' --> 'registered' (reason: user-requested)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (4/8): wait to get fully enabled
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (5/8): register
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (6/8): bearer
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (7/8): connect
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] state changed (registered -> connecting)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer3] couldn't start network: QMI protocol error (14): 'CallFailed'
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer3] verbose call end reason (3,2001): [cm] no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <warn>  [modem0/bearer3] connection attempt #6 failed: Call failed: cm error: no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] state changed (connecting -> registered)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer3] connection #6 finished: duration 0s, tx: 0 bytes, rx: 0 bytes
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.2716] modem["cdc-wdm0"]: modem state changed, 'registered' --> 'connecting' (reason: user-requested)
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.2957] modem["cdc-wdm0"]: modem state changed, 'connecting' --> 'registered' (reason: user-requested)
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.3155] modem["cdc-wdm0"]: modem state changed, 'registered' --> 'connecting' (reason: user-requested)
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.3373] modem["cdc-wdm0"]: modem state changed, 'connecting' --> 'registered' (reason: user-requested)
Feb 27 12:22:14 ercolano NetworkManager[700]: <warn>  [1740655334.3387] modem-broadband[cdc-wdm0]: failed to connect modem: Call failed: cm error: no-service
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.3389] device (cdc-wdm0): state change: prepare -> failed (reason 'unknown', sys-iface-state: 'managed')
Feb 27 12:22:14 ercolano NetworkManager[700]: <warn>  [1740655334.3470] device (cdc-wdm0): Activation: failed for connection 'Prepaid Contracts'
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.3482] device (cdc-wdm0): state change: failed -> disconnected (reason 'none', sys-iface-state: 'managed')
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.3560] policy: auto-activating connection 'Prepaid Contracts' (adcf9c04-57f3-4bca-b30f-b13877182103)
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.3580] device (cdc-wdm0): Activation: starting connection 'Prepaid Contracts' (adcf9c04-57f3-4bca-b30f-b13877182103)
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.3604] device (cdc-wdm0): state change: disconnected -> prepare (reason 'none', sys-iface-state: 'managed')
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.3646] device (cdc-wdm0): state change: prepare -> need-auth (reason 'none', sys-iface-state: 'managed')
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.3791] device (cdc-wdm0): state change: need-auth -> prepare (reason 'none', sys-iface-state: 'managed')
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect started...
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (4/8): wait to get fully enabled
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (5/8): register
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (6/8): bearer
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (7/8): connect
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] state changed (registered -> connecting)
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.4980] modem["cdc-wdm0"]: modem state changed, 'registered' --> 'connecting' (reason: user-requested)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer1] couldn't start network: QMI protocol error (14): 'CallFailed'
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer1] verbose call end reason (3,2001): [cm] no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer1] couldn't start network: QMI protocol error (14): 'CallFailed'
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer1] verbose call end reason (3,2001): [cm] no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <warn>  [modem0/bearer1] connection attempt #8 failed: Call failed: cm error: no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] state changed (connecting -> registered)
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.5425] modem["cdc-wdm0"]: modem state changed, 'connecting' --> 'registered' (reason: user-requested)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer1] connection #8 finished: duration 0s, tx: 0 bytes, rx: 0 bytes
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect started...
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (4/8): wait to get fully enabled
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (5/8): register
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (6/8): bearer
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (7/8): connect
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] state changed (registered -> connecting)
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.5766] modem["cdc-wdm0"]: modem state changed, 'registered' --> 'connecting' (reason: user-requested)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer2] couldn't start network: QMI protocol error (14): 'CallFailed'
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer2] verbose call end reason (3,2001): [cm] no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <warn>  [modem0/bearer2] connection attempt #7 failed: Call failed: cm error: no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] state changed (connecting -> registered)
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.6024] modem["cdc-wdm0"]: modem state changed, 'connecting' --> 'registered' (reason: user-requested)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer2] connection #7 finished: duration 0s, tx: 0 bytes, rx: 0 bytes
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect started...
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (4/8): wait to get fully enabled
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (5/8): register
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (6/8): bearer
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] simple connect state (7/8): connect
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] state changed (registered -> connecting)
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.6239] modem["cdc-wdm0"]: modem state changed, 'registered' --> 'connecting' (reason: user-requested)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer3] couldn't start network: QMI protocol error (14): 'CallFailed'
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer3] verbose call end reason (3,2001): [cm] no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <warn>  [modem0/bearer3] connection attempt #7 failed: Call failed: cm error: no-service
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0] state changed (connecting -> registered)
Feb 27 12:22:14 ercolano ModemManager[821]: <info>  [modem0/bearer3] connection #7 finished: duration 0s, tx: 0 bytes, rx: 0 bytes
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.6455] modem["cdc-wdm0"]: modem state changed, 'connecting' --> 'registered' (reason: user-requested)
Feb 27 12:22:14 ercolano NetworkManager[700]: <warn>  [1740655334.6474] modem-broadband[cdc-wdm0]: failed to connect modem: Call failed: cm error: no-service
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.6475] device (cdc-wdm0): state change: prepare -> failed (reason 'unknown', sys-iface-state: 'managed')
Feb 27 12:22:14 ercolano NetworkManager[700]: <warn>  [1740655334.6533] device (cdc-wdm0): Activation: failed for connection 'Prepaid Contracts'
Feb 27 12:22:14 ercolano NetworkManager[700]: <info>  [1740655334.6602] device (cdc-wdm0): state change: failed -> disconnected (reason 'none', sys-iface-state: 'managed')
Feb 27 12:22:18 ercolano ModemManager[821]: <info>  [modem0] 3GPP registration state changed (home -> searching)
Feb 27 12:22:18 ercolano ModemManager[821]: <info>  [modem0] state changed (registered -> searching)
Feb 27 12:22:18 ercolano NetworkManager[700]: <info>  [1740655338.6125] modem["cdc-wdm0"]: modem state changed, 'registered' --> 'searching' (reason: unknown)
Feb 27 12:22:24 ercolano systemd[1]: NetworkManager-dispatcher.service: Succeeded.

What the system journal said at 12:23, right as the status changed from 4G-with-exclamation-mark to 2G

Feb 27 12:23:15 ercolano ModemManager[821]: <info>  [modem0] 3GPP registration state changed (searching -> idle)
Feb 27 12:23:15 ercolano ModemManager[821]: <info>  [modem0] state changed (searching -> enabled)
Feb 27 12:23:15 ercolano NetworkManager[700]: <info>  [1740655395.1307] modem["cdc-wdm0"]: modem state changed, 'searching' --> 'enabled' (reason: unknown)
Feb 27 12:23:54 ercolano ModemManager[821]: <info>  [modem0] 3GPP registration state changed (idle -> registering)
Feb 27 12:23:54 ercolano ModemManager[821]: <info>  [modem0] 3GPP registration state changed (registering -> home)
Feb 27 12:23:54 ercolano ModemManager[821]: <info>  [modem0] state changed (enabled -> registered)
Feb 27 12:23:54 ercolano NetworkManager[700]: <info>  [1740655434.1455] modem["cdc-wdm0"]: modem state changed, 'enabled' --> 'registered' (reason: unknown)

[JR-Fi]

Ah, good additional description there. Then it’s possible that the network coverage isn’t that good in your area (it may change even within a building or room - signal just not getting through). Hard to say for sure but this is more likely to be something external like that as if the faulty behavior would be on the device side, I’d expect it to be more logical (you can always take a look at journalctl and systemctl logs, or see if modem antenna cables are attached properly). The exclamation mark (warning of problem, bad connectivity) and network are indeed connected as 4G calls are VoLTE calls and they use datanetwork to work. If not, modem reverts to 3G or 2G, if possible. See: Voice over LTE - Wikipedia

I don’t think it matters here, but just to be sure, have a look at BM818-tools app (or install it, if not present) and see if the VoLTE switch is selected there.

[Edit: Adding logs was good idea]

[JR-Fi]

Looking at the logs, it seems the several “no-service” mentions probably means in this case that it’s not getting a connection to network. If you want to check that, go outside and near(er) cell towers (but not too near as there may be blind spots) and see if problem persists (although theoretically network could still not give you stable connection if it’s overloaded or something, or your pre-paid subscription gets lower priority, so not 100% proof).

[jonsger]

I have checked right now and I do think VoLTE works for me at Deutsche Telekom network.

I disabled WiFi, did a download with wget --limit-rate=500k https://link.to/big-iso and started a call. The download did not get interrupted and continued with 500kbit/s.
2G/GSM based internet (EDGE) can download maximum 237kbit/s and there is no 3G/UMTS network in Germany anymore. So it’s save to assume that VoLTE is used.

Also the dial process is pretty fast which could indicate the use of VoLTE…

[JR-Fi]

Good to know. Modem limit is max 150M down and 50M up, if I recall, so depending on your service level, you could try even higher. And to be pedantic, VoLTE is Voice over LTE, so data transfer isn’t proof as such - you’d need to make a call to verify VoLTE (you just proved LTE data connection).

[Edit to add: If you want background on why VoLTE is such a mess, see under that wiki article’s heading “Device Compatibility Issues”, and of course search some of the old forum posts]

[Lliure]

@JR-Fi

have a look at BM818-tools app (or install it, if not present) and see if the VoLTE switch is selected there.

This gives me mixed results.

When I open the app, the VoLTE box is ticked.
However, when I look at the output of bm818-volte-check it says other stuff.

Here’s an old output log from 2023 when I enabled VoLTE

$ sudo apt install bm818-tools
$ sudo bm818-volte-check
BMRAT state not active
$ sudo bm818-volte
enabling VoLTE
chat:  Aug 28 19:06:08 AT+CGDCONT=2,"IPV4V6","ims"
VoLTE enabled
chat:  Aug 28 19:06:08 AT$QCPDPIMSCFGE=2,1,0,0
$ sudo bm818-volte-check
BMRAT state active  FDD LTE

And here’s what happens when I enable VoLTE right now

$ sudo bm818-volte-check
chat:  Feb 27 12:55:30 +BMRAT: EDGE
BMRAT state not active  EDGE
$ sudo bm818-volte
/usr/bin/bm818-volte
enabling VoLTE
chat:  Feb 27 12:55:40 AT+CGDCONT=2,"IPV4V6","ims"
VoLTE enabled
chat:  Feb 27 12:55:40 AT$QCPDPIMSCFGE=2,1,0,0
$ sudo bm818-volte-check
/usr/bin/bm818-volte-check: line 5: /dev/ttyUSB3: No such file or directory
No modem found

A few seconds later:

$ sudo bm818-volte-check
BMRAT state not active

Here’s what happens in the system journal when I enable VoLTE

Feb 27 12:55:41 ercolano kernel: wdm_int_callback: 9 callbacks suppressed
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: nonzero urb status received: -71
Feb 27 12:55:41 ercolano kernel: wdm_int_callback: 9 callbacks suppressed
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: wdm_int_callback - 0 bytes
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: nonzero urb status received: -71
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: wdm_int_callback - 0 bytes
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: nonzero urb status received: -71
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: wdm_int_callback - 0 bytes
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: nonzero urb status received: -71
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: wdm_int_callback - 0 bytes
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: nonzero urb status received: -71
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: wdm_int_callback - 0 bytes
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: nonzero urb status received: -71
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: wdm_int_callback - 0 bytes
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: nonzero urb status received: -71
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: wdm_int_callback - 0 bytes
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: nonzero urb status received: -71
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: wdm_int_callback - 0 bytes
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: nonzero urb status received: -71
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: wdm_int_callback - 0 bytes
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: nonzero urb status received: -71
Feb 27 12:55:41 ercolano kernel: qmi_wwan 1-1.2:1.4: wdm_int_callback - 0 bytes
Feb 27 12:55:42 ercolano kernel: usb 1-1.2: USB disconnect, device number 7
Feb 27 12:55:42 ercolano kernel: option1 ttyUSB0: GSM modem (1-port) converter now disconnected from ttyUSB0
Feb 27 12:55:42 ercolano kernel: option 1-1.2:1.0: device disconnected
Feb 27 12:55:42 ercolano kernel: option1 ttyUSB1: GSM modem (1-port) converter now disconnected from ttyUSB1
Feb 27 12:55:42 ercolano kernel: option 1-1.2:1.1: device disconnected
Feb 27 12:55:42 ercolano kernel: option1 ttyUSB2: GSM modem (1-port) converter now disconnected from ttyUSB2
Feb 27 12:55:42 ercolano kernel: option 1-1.2:1.2: device disconnected
Feb 27 12:55:42 ercolano kernel: option1 ttyUSB3: GSM modem (1-port) converter now disconnected from ttyUSB3
Feb 27 12:55:42 ercolano kernel: option 1-1.2:1.3: device disconnected
Feb 27 12:55:42 ercolano kernel: qmi_wwan 1-1.2:1.4: wdm_int_callback - usb_submit_urb failed with result -19
Feb 27 12:55:42 ercolano kernel: qmi_wwan 1-1.2:1.4 wwan0: unregister 'qmi_wwan' usb-xhci-hcd.4.auto-1.2, WWAN/QMI device
Feb 27 12:55:42 ercolano ModemManager[812]: <info>  [base-manager] port ttyUSB3 released by device '/sys/devices/platform/soc@0/38200000.usb/xhci-hcd.4.auto/usb1/1-1/1-1.2'
Feb 27 12:55:42 ercolano ModemManager[812]: <info>  [base-manager] port ttyUSB2 released by device '/sys/devices/platform/soc@0/38200000.usb/xhci-hcd.4.auto/usb1/1-1/1-1.2'
Feb 27 12:55:42 ercolano ModemManager[812]: <info>  [base-manager] port ttyUSB0 released by device '/sys/devices/platform/soc@0/38200000.usb/xhci-hcd.4.auto/usb1/1-1/1-1.2'
Feb 27 12:55:42 ercolano ModemManager[812]: <info>  [base-manager] port ttyUSB1 released by device '/sys/devices/platform/soc@0/38200000.usb/xhci-hcd.4.auto/usb1/1-1/1-1.2'
Feb 27 12:55:42 ercolano ModemManager[812]: Cannot read from istream: connection broken
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] QMI endpoint hangup: removed
Feb 27 12:55:42 ercolano NetworkManager[686]: <info>  [1740657342.0909] device (cdc-wdm0): state change: disconnected -> unmanaged (reason 'removed', sys-iface-state: 'removed')
Feb 27 12:55:42 ercolano ModemManager[812]: <info>  [modem3] connection to qmi-proxy for /dev/cdc-wdm0 lost, reprobing
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Releasing 'voice' client with flags 'release-cid'...
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Unregistered 'voice' client with ID '1'
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Releasing 'pdc' client with flags 'release-cid'...
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Unregistered 'pdc' client with ID '1'
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Releasing 'loc' client with flags 'release-cid'...
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Unregistered 'loc' client with ID '1'
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Releasing 'uim' client with flags 'release-cid'...
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Unregistered 'uim' client with ID '1'
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Releasing 'wms' client with flags 'release-cid'...
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Unregistered 'wms' client with ID '1'
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Releasing 'wds' client with flags 'release-cid'...
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Unregistered 'wds' client with ID '1'
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Releasing 'nas' client with flags 'release-cid'...
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Unregistered 'nas' client with ID '1'
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Releasing 'dms' client with flags 'release-cid'...
Feb 27 12:55:42 ercolano ModemManager[812]: [/dev/cdc-wdm0] Unregistered 'dms' client with ID '1'
Feb 27 12:55:42 ercolano ModemManager[812]: <info>  [base-manager] port cdc-wdm0 released by device '/sys/devices/platform/soc@0/38200000.usb/xhci-hcd.4.auto/usb1/1-1/1-1.2'
Feb 27 12:55:42 ercolano ModemManager[812]: <info>  [base-manager] port wwan0 released by device '/sys/devices/platform/soc@0/38200000.usb/xhci-hcd.4.auto/usb1/1-1/1-1.2'
Feb 27 12:55:48 ercolano kernel: usb 1-1.2: new high-speed USB device number 8 using xhci-hcd
Feb 27 12:55:48 ercolano kernel: usb 1-1.2: New USB device found, idVendor=2020, idProduct=2060, bcdDevice= 0.00
Feb 27 12:55:49 ercolano kernel: usb 1-1.2: New USB device strings: Mfr=3, Product=2, SerialNumber=4
Feb 27 12:55:49 ercolano kernel: usb 1-1.2: Product: Qualcomm CDMA Technologies MSM
Feb 27 12:55:49 ercolano kernel: usb 1-1.2: Manufacturer: Qualcomm, Incorporated
Feb 27 12:55:49 ercolano kernel: option 1-1.2:1.0: GSM modem (1-port) converter detected
Feb 27 12:55:49 ercolano kernel: usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB0
Feb 27 12:55:49 ercolano kernel: option 1-1.2:1.1: GSM modem (1-port) converter detected
Feb 27 12:55:49 ercolano kernel: usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB1
Feb 27 12:55:49 ercolano kernel: option 1-1.2:1.2: GSM modem (1-port) converter detected
Feb 27 12:55:49 ercolano kernel: usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB2
Feb 27 12:55:49 ercolano kernel: option 1-1.2:1.3: GSM modem (1-port) converter detected
Feb 27 12:55:49 ercolano kernel: usb 1-1.2: GSM modem (1-port) converter now attached to ttyUSB3
Feb 27 12:55:49 ercolano kernel: qmi_wwan 1-1.2:1.4: cdc-wdm0: USB WDM device
Feb 27 12:55:49 ercolano kernel: qmi_wwan 1-1.2:1.4 wwan0: register 'qmi_wwan' at usb-xhci-hcd.4.auto-1.2, WWAN/QMI device, 5a:b6:a0:76:25:6f
Feb 27 12:55:49 ercolano systemd-udevd[5151]: Using default interface naming scheme 'v247'.
Feb 27 12:55:49 ercolano systemd-udevd[5151]: ethtool: autonegotiation is unset or enabled, the speed and duplex are not writable.
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0] Opening device with flags 'version-info, proxy'...
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0] created endpoint
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0] Checking version info (45 retries)...
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0] QMI Device supports 30 services:
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    ctl (1.5)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    wds (1.67)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    dms (1.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    nas (1.25)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    qos (1.12)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    wms (1.10)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    auth (1.3)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    at (1.4)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    voice (2.1)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    cat2 (2.24)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    uim (1.46)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    pbm (1.4)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    test (1.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    loc (2.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    sar (1.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    ims (1.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    csd (1.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    ts (1.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    tmd (1.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    wda (1.16)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    csvt (1.1)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    imsp (1.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    imsa (1.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    coex (1.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    pdc (1.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    rfrpe (1.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    dsd (1.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    unknown [0x2d] (1.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    unknown [0x30] (1.0)
Feb 27 12:55:51 ercolano ModemManager[812]: [/dev/cdc-wdm0]    unknown [0x36] (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: <info>  [device /sys/devices/platform/soc@0/38200000.usb/xhci-hcd.4.auto/usb1/1-1/1-1.2] creating modem with plugin 'broadmobi' and '6' ports
Feb 27 12:55:52 ercolano ModemManager[812]: <info>  [base-manager] modem for device '/sys/devices/platform/soc@0/38200000.usb/xhci-hcd.4.auto/usb1/1-1/1-1.2' successfully created
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Opening device with flags 'version-info, proxy'...
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] created endpoint
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Checking version info (45 retries)...
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] QMI Device supports 30 services:
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    ctl (1.5)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    wds (1.67)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    dms (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    nas (1.25)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    qos (1.12)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    wms (1.10)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    auth (1.3)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    at (1.4)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    voice (2.1)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    cat2 (2.24)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    uim (1.46)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    pbm (1.4)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    test (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    loc (2.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    sar (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    ims (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    csd (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    ts (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    tmd (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    wda (1.16)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    csvt (1.1)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    imsp (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    imsa (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    coex (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    pdc (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    rfrpe (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    dsd (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    unknown [0x2d] (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    unknown [0x30] (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0]    unknown [0x36] (1.0)
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Allocating new client ID...
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Registered 'wda' (version 1.16) client with ID '1'
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Allocating new client ID...
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Releasing 'wda' client with flags 'release-cid'...
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Unregistered 'wda' client with ID '1'
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Registered 'dms' (version 1.0) client with ID '1'
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Allocating new client ID...
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Registered 'nas' (version 1.25) client with ID '1'
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Allocating new client ID...
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Registered 'wds' (version 1.67) client with ID '1'
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Allocating new client ID...
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Registered 'wms' (version 1.10) client with ID '1'
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Allocating new client ID...
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Registered 'uim' (version 1.46) client with ID '1'
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Allocating new client ID...
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Registered 'loc' (version 2.0) client with ID '1'
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Allocating new client ID...
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Registered 'pdc' (version 1.0) client with ID '1'
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Allocating new client ID...
Feb 27 12:55:52 ercolano ModemManager[812]: [/dev/cdc-wdm0] Registered 'voice' (version 2.1) client with ID '1'
Feb 27 12:55:52 ercolano ModemManager[812]: <warn>  [modem4] couldn't query SIM slots: QMI protocol error (94): 'NotSupported'
Feb 27 12:55:52 ercolano ModemManager[812]: <warn>  [modem4/sim4] couldn't load operator identifier: Couldn't get home network: QMI protocol error (16): 'NotProvisioned'
Feb 27 12:55:52 ercolano ModemManager[812]: <warn>  [modem4/sim4] couldn't load operator name: Couldn't get home network: QMI protocol error (16): 'NotProvisioned'
Feb 27 12:55:52 ercolano ModemManager[812]: <warn>  [modem4/sim4] couldn't load list of emergency numbers: uninitialized emergency numbers list
Feb 27 12:55:52 ercolano ModemManager[812]: <info>  [modem4] state changed (unknown -> disabled)
Feb 27 12:55:52 ercolano NetworkManager[686]: <info>  [1740657352.8584] modem["cdc-wdm0"]: modem state changed, 'disabled' --> 'enabling' (reason: user preference)
Feb 27 12:55:52 ercolano NetworkManager[686]: <info>  [1740657352.8593] manager: (cdc-wdm0): new Broadband device (/org/freedesktop/NetworkManager/Devices/9)
Feb 27 12:55:52 ercolano NetworkManager[686]: <info>  [1740657352.8609] device (cdc-wdm0): state change: unmanaged -> unavailable (reason 'managed', sys-iface-state: 'external')
Feb 27 12:55:52 ercolano NetworkManager[686]: <info>  [1740657352.8626] device (cdc-wdm0): modem state 'enabling'
Feb 27 12:55:52 ercolano NetworkManager[686]: <info>  [1740657352.8677] device (cdc-wdm0): state change: unavailable -> disconnected (reason 'none', sys-iface-state: 'managed')
Feb 27 12:55:52 ercolano ModemManager[812]: <info>  [modem4] state changed (disabled -> enabling)
Feb 27 12:55:52 ercolano ModemManager[812]: <info>  [modem4] power state updated: on
Feb 27 12:55:53 ercolano ModemManager[812]: <info>  [modem4] state changed (enabling -> enabled)
Feb 27 12:55:53 ercolano ModemManager[812]: <info>  [modem4] 3GPP registration state changed (unknown -> registering)
Feb 27 12:55:53 ercolano ModemManager[812]: <info>  [modem4] 3GPP registration state changed (registering -> home)
Feb 27 12:55:53 ercolano ModemManager[812]: <info>  [modem4] state changed (enabled -> registered)
Feb 27 12:55:53 ercolano NetworkManager[686]: <info>  [1740657353.1183] modem["cdc-wdm0"]: modem state changed, 'enabling' --> 'enabled' (reason: user-requested)
Feb 27 12:55:53 ercolano NetworkManager[686]: <info>  [1740657353.1244] modem["cdc-wdm0"]: modem state changed, 'enabled' --> 'registered' (reason: unknown)

No matter what, the graphical bm818-tool app says VoLTE enable all the time.

@JR-Fi

or your pre-paid subscription gets lower priority

It’s actually a post-paid contract, and not exactly the cheapest option.
No idea why PureOS keeps claiming that the connection was pre-paid. It’s been that way since day one. I don’t know how to rename the entry.

@JR-Fi

see if modem antenna cables are attached properly

That’s a very good lead!
Turns out I actually had to disconnect the antenna cables twelve months ago when I exchanged the modem.

I remember being super extra cautious back then, and I recall double-checking whether the tiny plugs were firmly connected to the socket. However, there’s a good chance I still messed it up somehow. Thanks for the pointer!

Update: One weird error message that might count against the antenna hypothesis would be the following journal entry:

Feb 27 12:22:13 ercolano ModemManager[821]: <warn>  [modem0] network reject indication received
Feb 27 12:22:13 ercolano ModemManager[821]: <warn>  [modem0]   service domain: ps
Feb 27 12:22:13 ercolano ModemManager[821]: <warn>  [modem0]   radio interface: lte
Feb 27 12:22:13 ercolano ModemManager[821]: <warn>  [modem0]   reject cause: ue-identity-not-derived-by-network

I wonder what the reject cause ue-identity-not-derived-by-network might mean, and what device generates that message.
There’s only one single mention of that same error message on Kagi.

[JR-Fi]

That log looks very interesting, very good digging - I wouldn’t have thunk to suspect that. Ay, USB related messges could indicate that the card is not seated properly or some similar physical problem. The ttyUSB3 should be automatically created when modem is detected. Beyond that, this may be more someone else’s area of expertise.

[JR-Fi]

@Lliure

I wonder what the reject cause ue-identity-not-derived-by-network might mean, and what device generates that message.

I don’t know about the cause but it’s one of the standard network messages: LTE Release Causes - Telecompedia

[Xeda]

Isn’t it a carrier thing? I travel to Germany often, exactly your area, and I am almost all the time on 4G, roaming, all good.