Never permit anyone to cross path of moving door.
Garage door closes then opens liftmaster.
The opener s force setting may not be set correctly.
Chamberlain liftmaster professional 1 2 hp garage door opener that tends to open part way say 12 inches or so then stop.
Your garage door is programmed to travel a certain distance before it closes.
To reconnect the garage door to your liftmaster garage door opener manually close the garage door pull the emergency release handle down.
These steps should fix most doors.
This will cause the trolley to move into position and reconnect to the garage door.
The simple stuff if the garage door connected to your liftmaster opener only opens part of the way or it begins to open but then reverses check the track and the surrounding area for any objects.
Now press the remote control.
Close the garage door with the opener and watch it closely as it closes.
Liftmaster uses the protector system which projects an invisible light beam across the door opening and automatically opens the door if something someone crosses it s path.
Years ago garage door openers were required to utilize safety sensors to prevent doors from closing on small children.
Make sure the small light on each sensor is lit and not flickering.
Anytime the main light flashes 10 times and the door reverses to the open position it is a door sensor problem.
Always keep garage door in sight until completely closed.
The force setting tells the opener how much resistance the door should provide and if the opener detects more than is allowed the door will reverse.
As is the case with so many issues at the home there s no one reason why your garage door closes then opens.
Tweak them a bit.
Try opening the garage door with the remote and see what happens.
I hit the control agian and sometimes it will go back down and raise agian and read more.