Modbus tcp error

Hello,

I am trying to read data from Modbus tcp but I receive this error:

"Error: Modbus exception 3: Illegal data value (value cannot be written to this register)"

Thanks and regards.

You say you are trying to read data but the error suggests you are trying to write data.

Are you trying to write to a read-only address or an address that does not exist?

Have you tried reading simple registers that you definitely know exist?