I have a two old Liftmaster 1345 garage door openers, one for each side. The wall button (and of course the remote) of one of them has stopped working. The door will not go up and the motor will not turn on. The wall button is a regular doorbell button (no "lock" feature) and the light in it is now dim and flickering. The working door's button has a solid light.

I tried turning the power to it off and back on but no luck. Nothing is blocking the protector sensor and its LED light is solid. I also tried releasing the door from the motor to make sure it wasn't jammed.

Any other ideas? Thanks!

Sounds like a short in the opener unit. Take the cover off and make sure a critter hasn't been dining on a wires inside or living in there to keep warm.