They are misaligned this is the most likely problem and the most common issue with garage door openers.
Garage door closes and reopens immediately.
If the garage door does not close completely or begins to close and then opens back up again the down limit switch needs.
If your garage door won t open or close the problem could be a bent track a broken torsion spring or a bad capacitor int he motor housing.
The sensors are dirty wipe lenses with a clean soft cloth.
Your garage door is programmed to travel a certain distance before it closes.
This is almost always the result of a dirty or obstructed safety feature.
If it closes before that distance has been traveled it thinks something is wrong and it reopens to help prevent any damage or safety risk.
It goes partway down reverses direction and goes back up again.
As these wires short against the housing the electrical impulse causes the door opener to activate.
But changes in weather conditions can causes your garage door components to shift or contract.
If you re craftsman chamberlain etc garage door opener is closing and then opening up its likely a common problem related to the stop limit mechanism.
You push the button to close the garage door.
The symptom of this is a garage door that is in constant motion opening fully then immediately descending only to start the same cycle again.
If it closes only partway the safety sensors are usually responsible clean the lenses or realign them and make sure there are no obstacles blocking the beam.
There may also be loose wire connections inside the button housing itself.
Close the garage door with the opener and watch it closely as it closes.