DIAGNOSIS This is a general overheating error. The exhaust vents on the top and rear of the unit are blocked, or the internal thermal fuse has tripped.
FIX Move the air fryer immediately. Ensure it has at least 5 inches of clearance on all sides, especially the top and back. Clean any dust or grease from the vent slats with a dry brush. Unplug it for at least 60 minutes to let it cool and the fuse reset.
IF THAT DIDN'T WORK The thermal cutoff fuse may have failed permanently. This is a safety component on the main wiring harness near the heating element. It requires a multimeter to test and a soldering iron to replace.
HEADS UP Never run the unit under kitchen cabinets or in a confined space. It needs massive airflow.