Look for an aluminum valve block behind the drive motor. One or two of the valves will have a small knurled **** sticking out, push it in and turn 1/4 turn to lock in.
It may be located somewhere else but it will be in the tractor compartment in a valve block. This is probaly your issue or as you said a faulty lower switch if it doesn't have variable lift (single speed lift/lower) if it is variable there will be a pot for lift and lower and no switch so that wouldn't be the cause.
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