Hello,
We are trying to test our custom board with nRF9161 in a new location, so we bought local SIM cards (Yettel, Serbia) here. These are not special nb-iot SIMs, just prepaid SIM cards with lot of 4G GBs. The salesperson assured us that the card will work in a phone and in a 4G modem as well.
Before inserting into the board, I tested the SIM in my phone and it works fine.
The problem is that the our software on the board fails to connect to LTE network. Here are the commands we tried from the Zephyr console:
uart:~$ at at%xsim?
%XSIM: 1
OK
uart:~$ at at%xiccid?
ERROR
uart:~$ at at+cfun=4
OK
uart:~$ at at+cgdcont=0,ip,internet
OK
uart:~$ at at+cgauth=0,1,"yettel","gprs"
OK
uart:~$ at at+cfun=1
OK
uart:~$ at at+cesq
+CESQ: 99,99,255,255,255,255
OK
uart:~$ at at+cereg?
+CEREG: 5,0
OK
uart:~$
As you see, +CEREG: 5,0 means that SIM is "Not registered. UE is not currently searching for an operator to register to."
We replicated the APN setup from the phone but that doesn't help.
The boards from the same build batch, but with a special nb-iot SIMs connect to LTE and to Nordic cloud just fine in our USA lab.
Could somebody has an idea what could be wrong?
Regards,
Sergei