ID 3 is correct for SMA inverters.
Please send me number of registers and description.
for example solar production - 30529
PS test your connection using program: http://en.radzio.dxp.pl/modbus-master-simulator/
how to use is it explained on this page:
https://www.sma-sunny.com/en/how-to-test-the ...

Hello!

Plugin works with SMA Sunny Tripower inverter, 8 parameters are mapped:

• Solar Production

• DC Voltage

• Active Power AC

• Active Power DC

• DC Current

• Active Power L1

• Active Power L2

• Active Power L3

https://github.com/doopa75/SMA-Inverter-ModbusTCPIP
Enjoy!