You should have a manual crank ability on that to get it off the truck. Should be located by the switch that runs the legs up / down. Hopefully the handle for this is still with the unit.
It sounds like the battery may be dead, have a bad connection to either the positive or the ground as well.
2016 Pinnacle 36REQS
2014 Ford F-350 6.7 4x4 CC LB Dually
Mike & Chelle, My kids when they decide to go with us.