Do you have shore power? If not, chances are that the trailer battery was discharged by the "phantom loads" and you're facing a dead battery. It only takes 3 or 4 days for a typical single battery system to discharge below the "minimum level" of around 10.5 volts, rendering everything in the trailer inoperable.
Now, if you're connected to shore power, there may be other issues, but if you're in a storage lot without power, your battery is dead.
2015 F250 6.7l 4x4
2014 Cougar X Lite 27RKS