It seems I might have led you astray with my previous answer. :shock
The vx2 displays can show a DSC position on the screen. Here is a link to a pdf file describing the function. The example used is with our discontinued FM3000, but the DSC NMEA sentences and connections to your Icom should be the same.
Thanks, we have that diagram. It still will not show a radio-generated DSC call, and we can see the data coming in on the Port 2 monitor. Could there be an issue with the nmea versions? We think the M604 uses nmea 3.0.
The Vx2 supports DSC but not DSE sentences. Ensure you are sending the support sentence. If you are and it shows clearly in the port monitor of the Vx2, then it must be a problem with matching the NMEA 0183 versions. You might change the radio to NMEA Version 2 and verify that the Vx2 is setup for NMEA 2.0 in the port setup.
I'm back at this again after a short break. We are getting the data to the VX2 through an Actisense multiplexer, everything connected on the system shows good data being received. The VX2 is getting good data from an LS6000 through the multiplexer but nothing from the Icom. I sent an email to Actisense, they do not output NMEA V3, plus, they also said that the DSC sentence from the Icom, which is V3, is the same as V2, and should pass through the multiplexor ok.