Did you flash a new firmware?
If not, I don’t see a reason why they wouldn’t connect anymore unless the antenna is disconnected or something changed on AWS side.
Testing shows the devices work with TTN but refuse now to connect to AWS IoT Core. It appears AWS may have changed something that makes the lib incompatible in some way.
I did message you also on Discord.
I have 50 + devices in the field if these are power cycled the stop.
AWS cannot “just change something” in the LoRaWAN protocol to make this happen.
The only thing I can think of is that they block devices with LoRaMAC stack version 1.0.2. That’s what the library is based on.
There is no easy solution if that is the case. There is no version of the library that supports LoRaWAN stack V1.0.3 or V1.0.4.