Hi,
From what I can see, in the brain, you are using the address value of 1 and cfg# of 0.
The address in the brain dialog is actually the offset index from the start of the CFG#0
So try address 0 and see how you go.
Also get it communicating with Mach3 first by using the Test page, accessed from the Modbus config plugin
Cheers,
Peter.