Welcome to the site.
Does the door come back down or stay part way open when it stops?
If it stays part way open, does the motor keep running for a few seconds.
Have you checked the rollers are all free and turning and don't jam up stopping the door.
Have a look at the spring or springs to see if one is broken.
Pull the handle that disconnects the door from the motor chain and see if the door will open by hand.