I would say the cam follower pin i under the cover is worn out. Not unusual since it gets very little lube and it is soft metal. Easy to fix, just remove the top cover, drive out the old pin and drive in a new one. I always replace them with a piece of drill bit and have never had any issue even though some say it just causes the cam to wear but after many years and tractors I have not seen it yet.
Sometimes you can wiggle and hold side pressure (front, back, up and down) against the position control lever and can get the lift to work, sort of a test that sometimes works.