Now is the point in time where you gain a personal knowledge of the fuse, wires, switches and motor of your tongue jack.
You get to start by removing the fuse and reinserting it.
Check the tightness of the screws from the fuse to the motor.
Check the cleanness of the wire lugs and switch terminals.
Check the switch for an odd feel when actuated.
Check the gears(if any) and lubrication.
When everything checks out okay is when you find out why some of us are bald, some to white hair and some to whipped out the plastic so often it melts.
Sometimes the problem will manifest itself and stops forever but more often you will end up checking everything over and over until you find the problem.
Changing out suspected bad parts is sometimes the easiest procedure but it can be very, very expensive. Mechanical switches are a weak link fortunately they are usually inexpensive and if you can't find the problem, it may be worthwhile to change it out. Motors are most often the next weakest link. And ask anyone who has purchased a motor
from a dealer to replace a Ford window lift motor used in a Kwikee step.
All you can do is persevere.