DIAGNOSIS The close-limit setting is too short, causing the door to try to travel past the physical floor stop. The opener senses excess force and reverses.
FIX Adjust the close limit. On the motor unit, press and hold the 'Learn' button until the LED blinks. Immediately press the 'Up/Down' arrow button. Let the door close. Just before the door touches the floor, press the arrow button again to set the new close limit. The door will stop. Press the arrow once more to confirm.
IF THAT DIDN'T WORK The problem may be excessive down force. Check the down force adjustment dial on the side of the motor unit. Turn it counterclockwise slightly to reduce the force. Test close and repeat the safety reversal test with a 1.5-inch block.
HEADS UP A binding door can cause the same symptom. Disconnect the opener and manually operate the door. It should move smoothly with minimal effort. Sticking or binding points must be fixed before adjusting opener limits or force.