Leaving the inverter on in storage WILL run down the house batteries rather quickly. If the house batteries are flat, most times the onboard charger will not recharge them. Use a stand-alone charger to recharge batteries to at least 1/4 charge, then the onboard charger works. There are several items that draw power when MH is in storage if you don't use the disconnect switch or remove the neg. battery cable. Mine will discharge the house battery bank in 5 days unless I disconnect them.
Try starting the genset with the drive motor running. You may need to use the coupling switch to link house and chassis batteries.
#2. How long since you changed the air/ water separator filter desiccant cartridge? This is, IMO, the most common cause of air system problems.
2000 Winnebago Ultimate Freedom USQ40JD,
ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG 11B5MX,Infantry retired;Good Sam Life member,FMCA." My fellow Americans, ask not what your country can do for you, ask what you can do for your country. John F. Kennedy