If shore power is feeding converter (via main AC panel circuit breaker OR via a 120V AC outlet) then generator will also feed AC power to converter provided generator is supplying AC power.........
*either circuit breaker(s) on front panel of generator have tripped,
*generator power cord is not plugged into rig power outlet (if it has to be physically plugged in)
*OR the transfer switch is 'stuck' on shore power position (not switching input feed to generator side).
As 'pianotuna' questioned........do any other AC appliances work (microwave, outlets etc.)?