I just aquired 5 Pro RF Boards for a LoRa communication project. After plugging the boards into my Computer (Windows 10) they registered properly as COM Port devices. At some point I even made them Communicate with the sample project provided here
After flashing on the sample project from sparkfun and doing minor changes to it, the boards became inresponsive. They are no longer recognized as COM Port devices. This happened the same way with four of the five boards and at this point I'm afraid to plug in the last one without knowing what's going on.
I followed the steps for troubleshooting the SAMD21 Dev boards here but it didn't change a thing.
The code still seems to execute on the board, since the status LED illuminates shortly after startup, but the board doesn't show up in the Arduino Ports or in the Windows Device Manager.
Is there any way to do a chip erase on the Pro RF Board or to flash the bootloader again? Why are the board failing ?