Is this a 30- or 50-Amp Coach? Is there some kind of "load shedding" device?
I ask because this A/C is acting like my neighbor's house unit did, when one leg of the 240-VAC AC power supply went out.
So, with that in mind, what is the Voltage at the A/C when it's trying to start?
And, as you check circuits, you'll verify the Hot Side/Black wire connections at Shore Tie, Breaker Panel, etc. Pay equal attention to the Neutral Side/White wire connections!
Finally, any "punch down" junction box is suspect.