What causes a garage door opener not to work?

A garage door opener may not work due to several causes including power failure, remote battery dead, safety sensor misalignment, locked door, broken spring, or motor failure. Most common cause is power issue, opener unplugged, outlet no power, circuit breaker tripped, or power outage, check outlet with lamp. Second common cause is remote battery dead, replace battery and try wall control, if wall control works but remote doesn't, battery or programming issue. Third cause is safety sensors at bottom of door tracks misaligned, dirty, or blocked, sensors have LED lights that should be steady, if blinking, sensors misaligned or blocked, clean lenses and align. Fourth cause is door locked or in lock mode, manual slide lock engaged or vacation lock on wall control activated disabling remotes. Fifth cause is broken torsion spring, door becomes heavy and opener cannot lift, try opening manually by pulling emergency release cord, if heavy, spring broken needs professional repair. Sixth cause is travel limits and force settings incorrect, opener may think door already open or closed. Seventh cause is stripped gears or worn drive chain/belt causing grinding noise but no movement. Eighth cause is logic board failure due to power surge. Ninth cause is remote not programmed, reprogram using Learn button. Check these systematically to diagnose.