Suddenly "Net denied"? (at+creg code 3)

IoT Modules LPWA Module
1

Hi Forum and Support,
We are using SIMs from 1NCE in Europe (LTE-M and 2G). Since several years this worked stable (about 2 - 60 registrations to the network per day with deep sleep/power in between) but recently some devices (very rare, but regular) get code “3” on at+creg ( = ‘Net denied’), although SIMs are valid, signal good and Network should accept the SIM for roaming. Normally after this message the device powers down the modem and waits for the next timeslot (15 min to 12h), but gets same result for often several days. Sometimes, after a few days or if location is changed to another cell it works again.

This very difficult to debug, because rare and always far away. Anybody else with the same effect?

Could it be a solution, to wait after at+creg gets 3 for some time or to force a new search with at+cops=0?

Thanks for your help! Jo

2

Maybe I found the reason: https://support.emnify.com/hc/en-us/articles/7116269647260-Network-Attachment-with-NB-IoT-networks

3

Your SIM may include the User controlled PLMN selector with Access Technology file. The command to read it:

AT+CRSM=176,28512,0,0,0

If it’s there, you may be able to overwrite it with your own preferences.

If you know exactly which network you want to register with, you can always use the AT+COPS=4,2,<PLMN> command.

From 3GPP 27.007:

4 manual/automatic (<oper> field shall be present); if manual selection fails, automatic mode (<mode>=0) is entered