Same problem on Genie Pro 88 can be caused by a burned (high resistance) contact on the middle relay. Check it with a multimeter. Can be fixed by carefully removing the cover on this relay and sanding the contacts with fine sandpaper. Then bend the moving contact arm so that it applies more force when closed. Check again with the multimeter before reassembling.

A friend called me about his neighbor's opener, opening but not closing, it's a 23 yr old Pro88. Of course a repairman told them (over the phone) it was gone and $700.00 for a new opener, I figured it was toast.

I found this site and the comments regarding the ground screw(s). The inside was clean, only one cobweb and not dirty at all.
All the screws for the green (ground) wires were tight and good continuity from the chassis to the other end of the wires.
I removed the screw for the sequencer board (it was tight) and examined the board itself. I noticed the parts of the solder pads that were underneath the screw head were "smashed", with a dull rather than shiny finish.

I re-flowed the solder, adding just a little to each pad, reinstalled the board and the opener was back in full working order.

Hi Guys - how cool are the answers! I had the garage guys here twice, garage door opens but won't close (Genie Pro 1/3) probably installed just after the floods/Noah.
Read this stuff, got on the ladder (AGAIN! 2nd week now) loosened and tightened the big bugger bolts that hold everything in place, you can't miss them, 4 big flathead screws on all four sides (once you've taken the covers off, dummy - the back section).

But the clincher was following the wire from the sensor (you know, the little 'finger' that bends where the garage door needs to stop?On the big rail that goes from engine to wall). I followed the wire to a little mother-board that takes all the darn wires. I tugged at it gently and it almost came out, so I rammed it in harder/deeper back into its hole with nose-pliers. ( I suspect this is where another commentator, above, said "solder the bastard in for life") I also clenched, with the nose pliers all ends that I could see had mini-clamps and lo and behold - the darn door works perfectly again. Tomorrow I'll solder it properly as it will probably come loose again from radical vibrations of engine, Genie-pro SCREW-DRIVE ain't known for it's silent operation. Hahahaha - got to feed the kid, cheers good people of garage-door-land
Onto the next flood!