I have a Schneider ion 7750 power meter that integrating Modbus TCP.
The Generic Modbus tester the points read great. But read incorrectly in Niagara Modbus TCP network.
I'm assuming the Generic Modbus tester is Modbus Master/Client and the Schneider Ion is a slave/server, so the Niagra is the Master/Client.
I'm assuming that you can read the data, but the wrong data value is read, probably from an adjacent register, one higher or one lower.
When changing from the Generic tester to the Niagra, the Schneider slave register/addresses do not change in the Schneider, so the manner in which the master/client requests the data must be different. This is not uncommon, it's just the implementation of Modbus.
Try a request using a register/address one above or one below the address you are using now, and see if the correct appears. Use the same technique, subtracting or adding one to the register/address for the rest of your data.