No cellular connection with new SIM on 3 in UK

I’ve just returned to my Librem 5 after not using it for some time. I put a new pay-as-you-go SIM from three into it, but I can’t get any cellular connection. The SIM is activated and works in another phone. I have updated all the software. My symptoms:

  • The cellular signal strength indicator has an orange exclamation mark [UPDATE: I’ve realised this goes away when I turn mobile data on so it’s probably not relevant]
  • The network name keeps randomly changing to other networks - it shows “3 UK” when I first switch on but then changes after a minute or so to another network. Toggling cellular off and on again via the pull-down quick access menu temporarily restores it.
  • Attempts to send a text message fail with “Error sending SMS to …”
  • No texts are received

I did use a 3 SIM in the phone a few years ago when I first had it, but that SIM is no longer active hence the new one.

Does anyone have any suggestions?

What VoLTE setting?

Are you registered properly with GCHQ?

  1. Are you actually located in the UK, or are you roaming in some other country while using the 3UK SIM? (If the latter, is a data add-on required? Is the country you’re roaming in included?)

  2. Is the modem in your Librem 5 the European variant (BM818-E1)?

  3. Do the APN settings shown in the L5’s mobile network settings match what Three UK publishes?

  4. Do the SMS and MMS settings displayed in Chats match what Three UK publishes?

In reply to “amarok”:

  1. I am in the UK - no roaming involved.
  2. How do I tell which modem I have? The “Modem Details” page says:
    Manufacturer: QUALCOMM INCORPORATED
    Model 0
    Firmware MPSS.JO.2.0.2.c1.1-00032-9607_GENNS_PACK-1.351938.1 1[…”
    Note that it used to work (I had a Three SIM 2 or 3 years ago) so I assume it’s a suitable one.
  3. The Access Point Names screen in settings lists lots of entries. The one selected has:
    Name: 3
    APN: three.co.uk
    Username:
    Password:
    These settings seem to match a subset of the values on this link:
    https://community.three.co.uk/t5/Network/Three-APN-Settings/m-p/5373
  4. The SMS and MMS settings in the chat application did not match. I tried to change them to match the entries in the link above. I also added the phone number but it keeps disappearing whenever I exit the settings. When I entered them I got an error message “Chatty cannot process 11 MMSs”

and in reply to “irvinewade”:
I’m afraid I don’t know where to find the VoLTE settings

  1. The modem variant should be shown on your original invoice, or possibly on your order confirmation email. You can also check your Puri.sm account for it, where it might be listed. Other than that, you can partially disassemble the internals until you can see what’s printed on the modem itself. (If you ordered the phone directly from Purism and had it shipped to the UK, it very likely defaulted to the proper regional variant, unless you specified otherwise.)

  2. “match a subset” - Some fields are not shown in the Librem 5’s settings as they’re generally pre-programmed with no need to be set by the user. If you want to compare them, though, you can check in the system files here: /usr/share/mobile-broadband-provider-info/serviceproviders.xml

  3. Verify that the APN is selected, then try the SMS/MMS settings again. Enter them exactly as Three shows.

You might have some stuck messages. They can be unstuck; there’s a topic or two about that somewhere here in the forums.

VoLTE is controlled by a separate app called “BM818 Tool,” which is available in the software app, or by installing from the terminal with the command sudo apt install bm818-tools.

Launch the app, enable VoLTE, then do a mandatory reboot.

Out of curiosity, have you upgraded the OS to PureOS 11 /Crimson yet, or are you still on PureOS 10 / Byzantium. (See “About” in the main settings.) If you haven’t, there’s an upgrade tool available.

Upgrading is recommended, as Crimson is the official release now, and includes a lot of improvements. See: PureOS Crimson Development Report: January and February 2026 - Beta Released – Purism

The most direct answer to that that I found is: send the ATI command to the modem. The output includes the specific model i.e. modem variant. However whether you want to spend the time on that I don’t know. Tips for how to do that: Tips & Tricks · Wiki · Librem5 / docs / Librem 5 Community Wiki · GitLab

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