Similar thing happened to the wife and I the weekend before last. We got to the campground, hooked up but the AC compressor didn't kick in Ambient temp was 100° and inside the trailer reached 115°. Was unbearable so loaded the two dogs and we drove home leaving the trailer and driving back the next morning to tow it home.
Bought and replaced an AC replacement then switched them out last Friday. Didn't get to run the replacement it til yesterday. Kept the AC off til the ambient temp reached 100° this afternoon and inside the trailer was 105°. Turned the AC on and within a half hour the new unit dropped the temp to 85.
We're headed out this weekend for a week's camping. Happy wife...happy life.