When you say nothing works do you really mean nothing ? Yes, nothing works -
Does it even try to start or make a noise ? No. Won't turn over. house lights, tv, microwave, generator, slide-outs - nada
Headlights work ? No
Grounds are often the problem , I would look at the battery ground cables .
When the engine died were you doing any thing like trying to start he gen ? No. Trying all the "fix-its" from the service tech, he told me to start engine (which was running fine earlier) to see if the levelers would retract. started engine; it ran about 3 minutes then just shut off. wouldnt restart...