Diagnosis
This is almost always the safety reversal system. The door is meeting resistance, likely from a misaligned or binding door, or the force is set too low.
How to Fix It
Check the door balance first. Disconnect the opener using the red cord. The door should stay in place when lifted halfway. If it slams down, the springs need adjustment—call a door tech. If balanced, adjust the close force. Press and hold the 'Learn' button for 10 seconds until the LED blinks red. Press the wall button once. The LED will blink amber. Each subsequent press of the wall button increases close force. Stop when the door closes and seals properly.
If That Didn't Work
The safety reversing sensors may be misaligned or obstructed. Check the LED lights on both sensors. The sending eye should be solid, the receiving eye should be solid. If blinking, realign them.
Heads Up
Increasing close force is a safety compromise. If the door is heavy or binding, fix the root cause. The force should be the minimum needed to close.