Power Gear makes, or made, both full electric as well as hydraulic levelers (the hydraulic were powered by a 12-volt pump. If you're referring to the 12 volt electric version then your 12-volt batteries must be in top condition. These jacks use a lot of current and so weak batteries would not work properly or not at all.
Bob 2006 Monaco Camelot 40PDQ
US Navy Carrier Battlegroup 1959/1963
Summer in Colorado, Winter Texas Gulf Coast