It looks about 90 seconds to connect to Verizon with the Hologram SIM on the Boron LTE:
- External SIM selected
- Carrier (AT+UMNOPROF) explicitly set to 3
- APN set to “hologram”
I’m pretty sure AT&T never works with the Hologram SIM with LTE Cat M1. That appears to be the case with other hardware as well, not just the Boron, from searching their forums. That’s how I determined that you need to set the carrier.
Also make sure you do a Cellular.on() before issuing the three AT commands listed above. You should do it without enabling the system thread, otherwise the commands will silently fail because the modem is not fully initialized yet.