Old Dave

I've just started using X-Pilot and I'm having a real problem that I can't figure out. I loaded a flight plan in my FMS (Citation X), made sure there was a Vatsim controller available and using X-pilot I transmitted to JAX center and requested a radio check. He could hear me, but I could not hear the controller. I did see his text message in the X-Pilot screen but couldn't hear him. I've tried every thing I can think of, but nothing seems to work. Does anyone have any suggestions? Sure hope so!