this is a pallet jack. there is a switch at the top of the lift linkage stroke to shut off the pump power when all the way up. the arm on the switch can get bent, and the switch itself can go bad. locate that switch under the cover, and check by jumpering the wires. do not leave the wires jumpered as you will damage other components. Or better yet, get a crown tech to check it out, as you can get hurt trying to work a jumper wire while the truck may lift.