We had been using an AT&T M1-enabled SIM in one of our development units successfully for quite some time. After we upgraded that node to MFW v1.1.0, it is no longer able to connect to the cell network. We tried swapping SIMs around between devices with different firmware versions confirmed that any node still running MFW v1.0.1 is able to connect to the AT&T network using this SIM, and any node running MFW v1.1.0 is not. I put the SIM in one of our v1.1.0 nodes, loaded up at_client, and turned on as much output as I could. The relevant error when trying to connect to the network is this:
+CNEC_ESM: 33,0 +CNEC_EMM: 19 +CEREG: 2,"FFFE","FFFFFFFF",7,0,19,"11100000","11100000" +CEREG: 2,"0411","00F63F11",7,0,19,"11100000","11100000"
It gets the CEREG failure almost immediately and then just sits there doing nothing. (We waited 15+ minutes)
Again, this failure is using an official AT&T SIM that returns 2 to the AT%XOPERID command.
We are able to connect to the same AT&T cells using v1.1.0 if we put in an MVNO SIM (hologram).
What is the modem doing differently with and without the official AT&T SIM? Whatever it is doing, it's breaking something in our testing.
