Then, if the odds are good that the Dashboard Radio is powered through the House Battery "Salesman Switch", is the House Battery charged?
House Circuit Fuses are usually part of the "Load Center." On newer RV's that LC is probably a single unit containing
1. 120 VAC Breakers
2. 12 VDC Fuses
3. 120 VAC ==>> Converter/Charger
(4. maybe... 12 VDC ==>> Inverter)
Do you know where that Load Center is?
RV builders are notorious for hokey wiring. It could be connected outside the LC. It could originate at LC and still a fuse elsewhere.
Since this Radio includes a Backup Monitor Screen, when it WAS working, is some condition needed to make it work (like engine running, in gear, in reverse, the like) that isn't met right now. Or even a relay involved?
Most Class C's at least, have Dash Radio powered by either Chassis OR Coach.
Winnebago had a switch to let you choose.
Our first one was Chassis powered, so the Key had to be in ACC. Well, ACC also caused the Step to operate every time we opened the Coach Door. Wired it to Coach instead. Then the display became a parasitic load so I had to add a switch.
This Jayco has an ordinary aftermarket AM/FM/CD radio. If Engine is running, it'll play with the Coach Battery OFF. If Engine is OFF it won't play till Coach is ON. I don't know how it does it but it's sweet.