Hi there,
WOW, an ADAM … I haven’t seen one of those in a LONG, LONG time…
You got a lot going there, I would verify each stage and be sure the RS-485 polarity is not flipped.
Can you post a PIC of the setup. Also are you certain the lora gateway is properly configured for the stream of modbus data?
If it does work that would be very interesting.
HTH
GL 
PJ
Adam modules were all the rage back in the day , for all sorts of DATA acquisition and conversion. lots of AT 'ish like commands.