If this generator used to power the A/C,, And it no longer does so, there are two possible causes.
The A/C
The Generator
On the A/C make sure it works fine on shore power, MONITOR current using a clamp on ammeter on ONE of the power leads (White or black) that feed it.
NOTE: to access that wire you may need to open the power distribution panel, USE CAUTION dangerous voltages are present in this compartment.
ON the generator: Fuel supply is suspect #1,, Filter, Carb and Pump. Air cleaner is suspect #2
Susect #3 is..... Expensive
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