20 Most Recent liftmaster Chamberlain Garage Door Opener Transmitter 300MC - Page 8 Questions & Answers

Sounds like what you need acces too is inside the garage. If you don't have a pedestrian access door to your garage, or a window, or these are both locked, you are going to have to break something. Sorry to tell you that. Just pick the thing to break which is easiest to repair. Once inside, there is a mechanical release (usually a pull rope hanging from the opener main unit) that allows you to open the door manually. Then you can use the garage until you can address the problem. Good luck.

You have to first have your cars Homelink system learn your current remote (follow owners manual) THEN have the garage door opener learn the cars Homelink (push openers learn button then press the Homelink button you previously had learn your remote. Two learning steps required because the LiftMaster is a 'rolling code system'

Maybe it's the safety device that prevents the door closing if there is an obstruction. Many of these have a reflector mounted near the floor on one side and an infrared light on the other side. If either end it obstructed, the door won't close.

This is better left either to a pro or a phone chat of some kind. Thanks BB

Try to open it manually.