Depending on the model this blinking light might be a code telling you exactly what’s wrong with your garage door opener. If you don’t have a manual, it might be available online at the manufacturer’s website (you didn’t provide its brand / model and I can’t help you with that).
Manufacturers have different designs of sensors / electronic boards, different sensor light color coding, and different sensor light behavior (all wires must be connected for testing). Therefore, there’s no “miracle” cure that can be applied for all garage door openers.
Resolving your problem might be as simple as adjustment of misaligned sensors, checking for any obstruction that might be blocking clear line between the sensors (even a dirty spot on one of the lenses).
More difficult to trace would be some broken wire between the sensors and the garage door opener. It might not be possible to see this problem; you’d have to check wire’s continuity with electrical tester.
Electronic board could be also responsible for such behavior – you’d need a professional to test it.
Misaligned door tracks that don’t allow for smooth operation of garage doors could trigger reverse action. With garage doors FULLY CLOSED disconnect the opener’s handle and operate it up and down manually to see if travels without any problems.
Another thing could be “travel” and “force down” adjustment. If for some reason (maybe from vibration) they’ve moved from its original position, the garage door might be reversing automatically and immediately after you push the button to close it. There’s more about adjusting it in “garage door opener safety
Just click “comment” below if you have more questions or information about your opener.