Automatic Transfer Switch (ATS)

I have a 2021 Arctic Fox 811 cabover. The issue at hand is the generator will not provide 110 power to the rig. At first I thought it was an issue with the ATS not sure now. When connect to shore power the ATS has 128 volts leaving the box to the panel. When you disconnect shore power and fire up the generator there is .479 volts coming from the generator to the ATS generator connection and 0 volts going to the panel. So it appears there is an issue between the generator and the ATS box. I can't find a wiring diagram to find out what is between the generator and the ATS box. Any thoughts from the group?