we have a 2808 28C classic and it raised about 6 inches and quit and would not go up or down.
solution = in behind the panel where the switch and cable is but access that area from the lower shelf and there is a 15 amp fuse that blew. reason was the cable was on the far left and the hole through the floor for the cable was on the right and it wore though the plastic insert and cable shorted out at the switch.
prior finding this I pumped up the top and was informed by Midget RV to jump the solenoid to raise it . then to lower it have 1 person pull the cable and push the switch and another to open the bleeder at the front of the hydraulic pump. then when down reach in the front access at the battery box and tighten the bleeder.