Sofar Solar 110 KTL modbus communication via PLC

I am trying to control ActiveOutputLimit of the Sofar Solar 110 KTL grid-tied inverter through Modbus. I am using function code 6 to update activeOutputLimit to change the active power. Every time it shows a timeout error.
while reading Modbus registers is ok but writing is not working.

Does anyone have such a kind of experience and solution?