Start with the EASY stuff....you have a Monaco product. First, check the salesman switch by the FRONT DOOR. Flip it and see if that corrects the problem. I'm guessing it will. If not, see next.
To properly check things, you need to have a meter. If you don't have one, go to a local Home Depot or Lowes and buy one...every tool box should contain a meter.
Using the meter, ensure you're getting 110V from EACH leg of the 50amp service at the pedestal. If yes, then go next.
Remove the cover from the transfer switch. Plug the coach back into the pedestal and check for power on the pedestal side INSIDE the transfer switch. If yes, see next.
Open the electrical panel inside the engine compartment and check the two solenoids there. Are you getting power there? Let us know what you find.
DO NOT ATTEMPT TO REPLACE THE COVER ON THE TRANSFER SWITCH UNLESS THE COACH IS DISCONNECTED.....Dennis