Yes, there is a battery disconnect switch, and if your floor plan has a couch in the front, it is most likely under the couch when the big drawer is pulled out.
If your tongue jack works only when the trailer is plugged into the tow vehicle, your trailer battery could be totally shot, or disconnected.
"The time is always right, to do what's right." MLK
'08 34' Classic SO, '12 Ram 2500 4X4, 6.7L Cummins.