Could be a communication problem or a relay .
System wants to see , zero throttle signal from the TPS, so binding pedal due to carpet ; or as was my case rusted hinge. Others have reported switch trouble , not passing power to the system even though the light is on. With the no downshift displayed I'd, look at the switch. If the trans control showed 2 and no activation I'd think relay.
You would need a wiring schematic for your coach to track down a relay , if in fact it has one , but most do.
My coach has 2 relays for exhaust brake
and I don't know why , and hope I never have to find out.