Why does "LoRa.begin" fail here?

LoRaWAN is really designed as a method of lots of remote sensors feeding their data through a LoRaWAN gateway into a server that has an application you use to manage the data, this server can be on the Internet so it can be accessed remotely etc.

LoRaWAN is not really intended for 'control' since its not practible to issue quick and guaranteed control commands, its just not designed that way.

Maybe you need to recruit a knowledgeable professional to design your system ?