With the coach disconnected from shore power and the generator off go thru all terminals in both the transfer switch and breaker panel are ensure all are tight. Check both hot, neutrals and grounds.
If your coach is 50 amp powered you could have tripped one side of the primary breaker but the other side is holding the tripped side up so it looks like it's closed. Eye ball the breaker closely before you cycle it. If the two sides don't line up cycle it off then on and see what happens. Also ensure the breaker is firmly seated in the breaker buss bar. It just snaps into place and with the breaker panel covered removed you can actually pop it out and back into place. No different than the panel in your house.
Also pick up one of
THESE next time your near a hardware store. Makes troubleshooting and power off safety checks a bit easier.