Hi bobo13,
I noticed something strange with your configuration, when using Modpoll you are using FC03 (Read Holding Registers), while in Proview you are using the function code FC01 (Read Coils). You should probably change your command in Modpoll so it uses FC01 as well (use: -t 0). It might be better to simply set Mb.C[1], Mb.C[2] etc. to 1 and then poll them from Modpoll to check that you can read them correctly. This eliminates the possibility that something goes wrong when you read the pin state.
Also: if you attach a screenshot showing the status of the "Modbus_TCP_Client" it is possible to see if Proview is able to poll the device and get a reply.
Unfortunately I don't have my Arduino with me right now, so I can't