BRN402 Connectivity Scare - What we learned

Hardware
1

We had a situation with all of our fleet BRN402s (Device OS 4.1.0) in proximity to a single AT&T tower, where they were failing to connect with this registration "handshake" issue:

0000127979 [ncp.at] TRACE: > AT+CEREG?
0000127988 [ncp.at] TRACE: < +CEREG: 2,2

Upgrading the Device OS to V6.3.3 (latest) did not help.

Reloading our firmware did not help.

The devices attempt to register and connection using MNO profile 2. The following fix to our setup() routine to use MNO profile 0 did help but we did not roll the fix out to the fleet:

<snip>
   Log.info("  About to send UMNOPROF=0 MNO Profile Universal");
   int res = Cellular.command(10000, "AT+UMNOPROF=0\r\n");
<snip>

One caution, this is a sticky setting.

THE ACTUAL RESOLUTION was a willingness from AT&T to restart that tower. Their response: Our network team restarted the site and advised that the CAT-M for the sector has returned to normal baseline following the restart.

After the restart, all of our BRN402s were able to connect without issue.

This was a "wake up call" for us though regarding the BRN402s in the fleet and the probable need to plan for their retirement. I'll share more over time as we move forward.

2

Next day all devices were failing again and have been ever since. 404Xs are also failing on our local ATT tower. Everything works when we drive them up the road.

I am really stumped and welcoming ideas.