Janey, you never answered whether you have an EMS on board. That would be another panel on the wall behind the driver most likely. So I'll assume you do not have one unless you say differently.
Please clarify the “transfer switch”. Are you referring to the generator on /off switch?
No, the Automatic Transfer Switch or ATS. As others pointed out above on Phoenix units we have a automatic switch that monitors shore power and switches back and forth between shore and generator power. Mine is set to give the generator priority but I think this is programmable. And it looks nothing like a 'switch'. It is a shiny metal box about 6" by 8" with a contactor and coil inside to switch between 120 volt inputs.
What should happen is that if the switch senses 120 volt power from the generator it switches to that input and when the generator is not running it switches to regular shore power. When there is power at neither input then of course nothing happens.
Mine is located, as noted by 2 Frazzled, just behind the drivers seat. You can open it up and look to see if anything is obviously wrong but beyond that you will need a multimeter and test probes to see where the power is coming from. Please do not touch anything in the box while either the generator is running or you are connected to shore power.
If you have a multimeter (and feel comfortable working with high voltage):
1) Shut OFF the generator.
2) Test for power at the pole. If OK plug your cord into the pole and go to 3
3) Test the coach end of the cord with your meter. If OK plug the cord into the coach and go to 4
4) Open the ATS box and test for power at the shore power input. If power is present go to 5
5) Assuming you have power at the ATS input then test the output
6) If no power at the output then the ATS is faulty
At each point you test if you do not have power then the failure is upstream of that test point.
Since you reported all is fine with generator running I am going to assume the issue is at the ATS or upstream rather than at the power panel.
If there is no power at the ATS then the only other failure point is the coach receptacle which is inside of where the cord goes on the outside. Not sure where that is hidden on your coach.