RAK7431 returns "unsupported command" when trying to poll modbus register

LPWAN Nodes RAK7431
1

I have modbus connected with RAK7431. I setup a poll at every 20 seconds using below AT command.

at+transparent=0
at+pollperiod=20
at+addpoll=10:1C0323BF0001BDE7

I get following log:

SYSLOG:4:DTU Tx : 1C03232900015DCB
SYSLOG:4:LoRa Tx : C1002F00020B01

Interpreting response (i.e. LoRa Tx), I’m getting ERROR 1 which is “Unsupported command”. Why is that? What is wrong with poll instruction ?

If I set the transparent mode to 1 then I don’t get any Lorawan transmission (or SYSLOG) at all.

Any clue to figure out what is wrong will be much appreciated.