Hi Scott,
Can we get a tiny bit more information so we can hopefully help?
How do you know it is not charging on AC? Are you looking at the charge panel, are you using a multimeter, or are you observing the lights are getting dim?
Is this a new coach to you?
Did it ever charge when plugged into 15 amp?
Do you have a multimeter?
Do you know how to use the meter to check the voltage?
Have you checked for a battery disconnect switch? Maybe look inside the door by the steps.
Does the battery charge with the generator running?
Have you looked at the fuses and circuit breakers to see if anything is blown or tripped?