This set does not have a fuel tank (it uses the RV's tank) - where were you checking the vent?
This set is also microprocessor controlled. We need to see what Fault Code is being set.
Go to the genset and use the switch on the set itself.
Press 'Stop' 3 times within 5 seconds. The light in the switch will start flashing.
If the light flashes 3 times, pauses for 3 seconds, and flashes 3 more times, press and immediately release 'Stop' one more time.
This will put the controller into Fault Read Mode.
The light will flash (X) number of times, pause for 1 second, and flash for (X) number of times again. Count the flashes before and after the pause.
This will be the Fault Code.
Example: flash flash, 1 second pause, flash flash flash flash flash is a Fault Code 25.
There may be more than one Fault Code stored, so watch the light very carefully. If there is more than one code, it will display them all in order, and then start over again.
What Fault Code are you getting?