My 2011 Jayco Greyhawk generator starts right up if it only sits for a day or so but takes a really long time to get started after sitting for a few days. Is this normal?
Is the APU an Onan Microquiet? If so, it may be a fuel drain-back problem. This is not uncommon, and there is a cure. If you hold the stop side of the switch with it not running, this enables a "prime" circuit that will run the fuel pump to bring fuel back to the unit. It usually needs to get held for 10~15 seconds.