I know the jack system is 12vdc
Can you plug the camper into 120vac ( which you probably have an inverter/charger) and then run the jacks up/down/single/all?
If that doesn't work then it's probably a control board issue.
If your handy find your controller box and put a clamp-on ammeter on each jack leg and run it up and see what you read. The sum of the 4 legs should be under your max current draw. If 1 leg is high maybe just 1 jack is the problem.
Another way to do it is to unplug your jacks externally and plug in separately.
Run one up/down, then plug in one more jack and run all and see if it works, plug in another and so forth.
Good luck.