A bit of good news: my Boron is back to working perfectly on the internal SIM!
What did it: not sure, there may have been some issues with the network recently due to the massive winds we had on Sunday.
I have the sequence down to a science now: run my little credential setting / SIM setting / network setting program. Wait for the blue LED to blink at the end, so I know it’s done. Load and run boron-clouddebug.bin. Watch the serial output.
Network registration on the internal SIM is almost instantaneous. Much joy!
I’ve now tried the same sequence, switching to external Hologram SIM, APN “hologram”, AT&T modem preset, and also repeated for Verizon set up. No joy.
Switch back to internal SIM, clear the credentials, and the Boron works perfectly. I can now travel full circle. — just need to get that Hologram SIM to behave!
As always, thanks to the Particle team for the outstanding and rapid support!