It can be one of two things...the battery is done and won't hold a charge or the camper's converter isn't charging the battery when plugged into shorepower. If you have a voltage tester, the converter should be putting out at least 13.5V at the battery if it's working correctly. A fully charged battery should read around 12.6V when not plugged into shorepower. If the converter checks out, you could take the battery to as auto parts store and have it load tested to be sure.
Nights camped in 2013 - 55, 2014 - 105, 2015 - 63