I believe that my issue was that I did not have the object set up as a MU. It is working correctly now that I am using a source for the MU's. My apologies.

I have only ever successfully set up the RealVirtual interface to be a MODBUS slave (server), not a master (client). With the MODBUS server, you have to use the PLC to initiate the reads/writes. If you need the RealVirtual interface to be the master (client), I can't help you. If you are ok with using the PLC to initiate communications I can try and help you out as best as I can.