Right now I am at work…and the range extender is not available. T-mobile service is somewhat spotty here but not completely nonexistent. (On the other hand, perhaps I’m actually roaming here and never knew it.) Will have to try all this again from home.
I did find an apn though via google: fast.t-mobile.com. They also give an MMSC I’m not sure what to do with. [Edit–went to chatty and input both that and the APN in settings.]
As if that’s not enough I’m now getting an error when trying to scan networks. Couldn’t Scan networks QMI Protocol Error (3): internal
You might try disabling Mobile, then re-enabling it, or restarting, or moving around to get better signal.
I’m just going to have to try from home; I’m simply not seeing t-mobile at all. Meanwhile, I’ve got to make my other phone useable by putting the sim card back in it.
[Edit: The Android SurveillancePhone A12 seems to find t-mobile just fine.]
At home: Librem 5 detects AT&T and Verizon, and some numbered network starting with 3.
It does not detect T-mobile.
The same sim card, put into my Galaxy SurveillancePhone A12, has no trouble finding T-mobile.
Have you seen this thread?
Since @flanders51 is also using a range extender at home, you may find some tips there.
Except that I seriously doubt it’s my booster, because other phones work fine. Different carriers, too.
This one doesn’t pick up T-Mobile either at home or at work. Doesn’t even see it.
I will try other places where I am getting a solid T-Mobile signal (rather than three bars or so).
[Edit: There appear to be other goodies in that thread, so I am reading it.]
Ah, but:
(other phones) ≠ (BM818 modem)
I’m pretty much driven to the conclusion that I have a bad modem (and yes, it’s the replacement they sent me right after I got the phone). I’m partway through that other thread.
And it may be that ALL 818s are bad, or at least not good enough.
If you still have your other modem, try updating that firmware and seeing if it functions any differently from your current one.
Frankly: An interesting notion but of course I don’t want to switch back and forth on the modems unless I absolutely have to…those connectors are fragile.
OK I have an update.
Two locations not at my house and not near the spotty reception I have at work.
First location, 5 bars shown on my T-Mobile Samsung SurveillancePhone A12. Librem 5 doesn’t even see T-mobile there.
Second location, 300 yards away from a tower. FINALLY miracle of miracles the phone actually SEES a T-mobile signal. So selecting that and enabling the APN, I tried to make a call (this was 23:30 or so but it was to an automated number).
Instead of terminating the call instantly, the phone tried for about ten seconds, THEN terminated the call.
It should be noted that even there, the phone showed only two bars.
Have you checked your antenna connection? Maybe it was never quite reconnected correctly and has subsequently worked loose.
As things don’t seem to be working for you, I would be tempted to disable VoLTE and then re-enable it. I think though that you may need to reboot after each change of VoLTE setting.
Antenna connection: Are those the two fragile connectors on the modem?
VoLTE is worth trying again.
I should explain what I’ve done, in case I missed some setting.
Network Mode 2G, 3G, 4G (Preferred)
Network: Attempt to find Tmobile
Access Points: created and selected TMobile with APN fast.t-mobile.com
In bm818tool, VoLTE is enabled. Below the check Call button, it shows NONE. CBS enable is NOT checked.
Yes.
OK…I pushed on them a bit.
No difference, but I want to try again near the tower.
I’m still using your layout. 
I do hope your modem issue will be solved.
Well, I was asked to send a screenshot. Two days later I did. Now two days later I’ve heard nothing back. Which is pretty much what happened last time (information requested, sent, never heard from support again).
Dealing with support myself I know that patience is needed, but they will come back with a response. If I feel they are ‘forgetting’ me, I write a polite request for an update about the matter. Mostly I do this after give or take 10 (working) days.
Good plan.
OK, NEWS…Medium-Big news.
I heard back from support, and they requested (in essence) that I turn mmcli debugging on, then try to make a call and capture the journalctl. Very specific with the commands.
So I drove to near that one tower that almost seemed to work last week, but to a slightly different spot. Transferred my SIM card (I’m just waiting for the time I drop it somewhere nonrecoverable during this process…and in a car that’s very easy with something the size of a fleck of paint). Started the Librem5. Went into Mobile settings to select the network.
T Mobile was already selected.
I have NEVER seen that before. In the past, I’ve had to try to select it and maybe, maybe, IF I can even see Tmobile, I can select it and have it show up on the main mobile settings screen. But usually I select it and it does NOT show up on the main mobile settings screen.
So I tried to place the call…and it actually, So Help Me God, worked.
My first phone call on the Librem 5 was to the automated Naval Observatory Atomic Clock, +01 (719) 567-6742. (Nobody there to get annoyed at me calling.)
I kept the log file.
Of course this is the one time I wanted the phone to fail, so it worked. In order for support to see something useful it actually has to NOT work.
But this was easy to fix, or break, actually. I drove about half a mile. From there, if I pointed the phone in one direction, it wouldn’t let me set the network. A slightly different direction, and it did, but this time it failed to make the call after trying for about 15 seconds.
I kept that log file as well, different name.
I sent both to support.
ANYHOW:
This strongly suggests to me my modem is blind. probably, all settings are right (unless there is one that only mostly wrecks your ability to receive a signal). So either the modem is blind…or the antenna is bad…or somehow the connection between the antenna and the modem is bad. (And yes I did try pressing on the connectors a week or so ago.)