DIAGNOSIS The travel limit microcontroller thinks the door is not in the fully down position. The limit setting has drifted.
FIX Manually reset the down limit. With the door closed, press and hold the black button on the logic board until the LED blinks once. Immediately press and release the wall console close button. The opener will jog down slightly and reset the limit.
IF THAT DIDN'T WORK The magnetic travel sensor on the motor shaft may be faulty. It's a small black ring with a wire. Ensure it's securely plugged into the logic board (connector J8). A failure here usually causes a total travel fault, not just a false "open" reading.
HEADS UP Do not adjust the physical limit switches on the side of the opener. The 8500W uses electronic limits only.