I'm trying to troubleshoot a garden variety Liftmaster. The chain sprocket broke so I replaced the sprocket assembly. Now the door goes down less than a foot, then comes back up. The kicker is that the light on the motor doesn't blink at all, like it normally does when there is something blocking the door sensors. The door sensor lights appear to be aligned and functioning correctly. I can't find any information about this. When I search it, every result that comes up is where the motor light does blink when the door won't go down.
