You said if you jumper from Generator frame to chassis battery negative or to coach frame no joy but if you jumper from generator frame to coach (house) battery negative joy
Clean house battery connections.. On negative if you can find it clean both ends of that cable and see if that works. You have a poor connection on house negative lead not sure which end.
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times