How to fix a garage door when it won't open?

To fix a garage door when it won't open, you need to diagnose cause ranging from power issues to broken spring and apply safe repair, calling professional for high-tension parts. First, check power, as opener may be unplugged, breaker tripped, or GFCI tripped, so ensure opener lights on and outlet works. Check if manual slide lock on door track is engaged preventing opening and disengage it. Try wall switch, as if wall switch also fails, problem is opener or mechanical, not remote. Inspect safety sensors near floor for dirt or misalignment with blinking LEDs, cleaning lenses and aligning until solid, as sensors can prevent operation. Listen for motor humming, as humming with no movement suggests disconnected trolley from emergency release cord pulled, stripped drive gear, or door binding due to broken spring or off-track rollers. Try opening manually by pulling emergency release cord, usually red cord, and lifting door; if door is very heavy, won't lift, or falls, torsion spring likely broken and requires professional replacement costing 200 to 400 dollars due to danger of high tension, as door should lift easily when springs good. If door opens manually but not with opener, re-engage trolley by pulling cord toward door and running opener until it clicks. Check remote battery, reprogram remote via Learn button, and check lock mode on wall console that disables remotes, holding lock button to unlock. Check travel limits and adjust. Unplug opener 30 seconds to reset board.