Lights out

FYI, the screw terminal wire connections to the fuse individual holders can become loose and cause various 12 volt items to work erratically or not at all.
I found a loose screw connection at a fuse holder while checking fuses, got my AC thermostat working. Phew!

Thank you all. It was a loose wire from the fuse box. Found it and they are working properly now.

It is of course guesswork what is wrong until the problem is found.

I would probably start with checking grounds. With everything off, an ohmmeter should show a short circuit between the socket shell/ground line and the frame of the motorhome. (It'll probably be necessary to use a long lead on the meter to get to a good frame ground.) With that many lights on different circuits failing simultaneously, the ground connection seems to me like the main thing that is likely common to them all.

If the wiring runs externally within the frame rails, it might be worth inspecting it for damage, possibly from critters chewing on it.

check the wiring in the box for the pigtail.Sounds like some are loose