here is a wild guess (and not much more, a serial number would be a big help) you have a zapi controller that controls both the pump and traction, and you have (again a wild guess) traction motor brushes or the main contactor rusted stuck.
also, if this is the unit I think, it has a led that you can see when you look down into the joint that connects the control handle tot the traction unit when the handle is worked and the key on (handle position switch is light operated), and this unit has to have the handle see the up or down position before it will reset the static return to off circuits. of course from what we know so far, you could have a bad key switch.
there is a place in the zapi controller right were the control wires plug in for a handset or optional led to be plugged in to flash error codes.