Has it ever worked on generator power?
Not having a motorhome, I have read on these forums where some RV's, don't have a transfer switch, but you have to actually physically unplug your shore power cord, then plug in a generator plug in your compartment for the generator to provide power.
I have no idea if this applies to your situation, but let me see if I can find some of these threads, as I always believe in starting with the simple things first in troubleshooting.
Here is one recent on a Georgetown:
50 amp plug