The positive battery cable runs from the battery to a junction box under the camper. This is where the power enters the camper. Somewhere between the two, look for an inline fuse (probably 30 amp) or a short stop breaker (
looks like this).
Some short stop breakers will auto reset when the battery is disconnected and reconnected, some have a manual reset button, and some cannot be reset. They are available at RV dealers, most auto parts stores, and possibly stores where auto maintenance is performed.
What you are describing, sounds like a blown fuse.