When returning to MH found no power to wash machine,toilet,water heater,furnace,lights. AC power to refer,microwave and all outlets ok.
Let's see....Toilet, I assume is the 12 volts for the water pump
Water heater, can be BOTH 120 volts or propane, which needs 12 volts. Some WH are propane only.
Furnace, 12 volts and propane.
Lights, in most cases are 12 volts although I have ONE 120 volt fluorescent fixture in my coach
Washing machine, I assume 120 volts for the machine itself altho the pump that puts water in to the machine may be 12 volts.
Please verify what powers the washing machine since it seems that most of your other problems are 12 volt issues.
Since all of your outlets are working, this rules out the inverter/charger.
With nothing changing with the generator running, that seems to rule out the transfer switch and main breaker.
Depending on the washing machine, this seems to be a 12 volt issue, which is probably a fuse somewhere.