1 of 5 FiPys connect to NB-LTE

[cnopicilin]

Hello!

I bought 5 FiPys with expansion boards and antennas to build some IoT devices. After a few days of trial and error I managed to get 1 of the devices connected to our lab's NB-LTE network but the other 4 identical devices with same firmware, SIM card and code can't even find the network. I tried switching antennas and expansion boards, but the only working FiPy connects with any combination of parts while none of the others do.

Currently the functional part of my code looks like this (band, earfcn, apn hidden):

commands = ['AT+CFUN=0',
            'AT+CFUN=1',
            'AT!="clearscanconfig"',
            'AT!="addscanfreq band=BAND dl-earfcn=EARFCN"',
            'AT+CGDCONT=1,"IP","APN NAME"']

lte = LTE()

for command in commands:
    print(lte.send_at_cmd(command))
    time.sleep(1)

while not lte.isattached():
    time.sleep(1)

lte.connect()

Showphy shows randomly synchro state as CELL_SEARCH or FAST_SCAN for the devices with connection problems but the signal stays at 99,99 for >15 minutes with no change.

FiPy firmware: 1.18.0.r1
Sequans firmware: FIPY_GPY_NB1_37781

What could be the cause for such a weird problem? I assume the modem saves entered settings even through power cycles, but reloading the firmware should clear the settings, shouldn't it?

[cnopicilin]

I managed to get 4 of the 5 devices to connect yesterday, but this morning one of the previously working ones refuses to find any signal at all. I didn't make any modifications, so the FiPys might just be extremely unreliable.

[cnopicilin]

One of the working devices dropped connection the same day it finally connected and after a week of testing I haven't been able to reconnect it. It briefly found a signal two days ago but wasn't able to attach and has been silent since.

No idea what could be the cause, are there some commands outside of the LTE example on docs I should try? Also the 'AT!="zsp0:npc 1"' always returns "command unknown".

[cnopicilin]

After >18 hours of connecting the last device finally started working with the network. I have no idea what happened, because I made no changes to anything.

The only thing I can say is that the commands I have in the first post should be enough and be patient with it as it can take >24 hours to find signal and connect.