Find your garage door's emergency release rope. This release rope is red and hangs from the overhead assembly. Pull down on the rope to disengage the garage door's motor function to allow for calibration and repair.
Move over to the garage door and find its inner door handle. Hold onto this handle and use it to pull down the garage door. Do not yank down on the handle. The door is de-motorized and will fall downward rapidly if you do so, and you risk damaging the door. Instead, slowly "walk" the door down using the handle until the door shuts completely.
Return to the emergency release rope. Grab the rope and align it at a 45-degree angle, and pull it at this angle. This will reset and recalibrate the garage door's release arm into a horizontal orientation, which is necessary for proper operation and motorization.
Press the button on your garage-door opener. The door should no longer be stuck, and the recalibrated system will allow for the proper motorization of the door when the button is pushed.