How to fix my garage door opener?

Check sensors they can be off by a hair

A garage door that won't close via the remotes can be mis-aligned sensors but if that is the case you normally have to hold down the wall switch to force it to close. In my case none of the remotes would close the door. A simple tap of the wall switch would close it every time. In fact, the wall switch always worked normally except that it sometimes could not stop the door in the middle of an open or close. The sensors were aligned. I could tell by the LEDs on the sensors. The remotes would work once if the door was in a position for a long time (hours). Any further use of the remotes failed. The problem was a bad circuit board in the garage door controller. You can buy replacement boards from around $70-$100. I repaired mine. My unit is a LiftMaster 1245R, 41A5021-1C on the back label. These are the same as Chamberlain units.

To remove the circuit board first unplug your controller. Then disconnect the wires on the 3 terminals in the back (the side that faces away from the garage door). Remember which wires went on which terminals. Next there are 4 screws to remove on this back panel. With the screws removed the back panel will be loose but there is a wiring connector on the inside at the top of panel. Simply pull on this connector to separate the wires from the back panel. Now you can take the back panel (with circuit board attached) inside to work on the electronics.

There are 5 screws that hold the circuit board to the back plastic cover. Remove the to get access to the front of the circuit board. Looking at the component side of the circuit board look for capacitor C22. It is a 330uF 35V 85c part. It is the largest capacitor and is located on the left side right next to the transformer. Because it is located right next to the transformer and the transformer gets hot, the capacitor will eventually cook. Mine had a slight discoloration on the side nearest the transformer but otherwise looked normal. I replaced this capacitor, re-assembled the unit, and my garage door now works properly with all remotes.

I'm assuming you mean that it won't close, only open? If that's the case then your eye beams may need to be adjusted. The wall button can override the sensors whereas the remotes can not.