As to your issue.
1) Why no battery? Is it in a permanent site and never moved? You need a battery for your brakes to work if you disconnect while towing.
2) What is going on with those battery cables? They are HOT when the camper is plugged in. If they are laying on the frame (and not wrapped in electrician's or splicing tape) they can short out to the frame and fry your converter.
3) You have a 55 amp converter. Sounds like it is not working. It could have been fried by shorting out the battery cables (above) or it could have "just failed." (It happens).
4) Wall outlets are GFCI so check for outlet "trips" by pressing the reset buttons and see if the power comes back on at the outlets. They may have tripped as an unrelated issue with park power.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW