DIAGNOSIS That's an automatic overheat protection trip. The fan or heating element area is probably clogged with accumulated grease and crumbs, causing poor airflow and excessive heat buildup.
FIX 1) Unplug and let it cool for at least an hour. 2) Remove the basket and the inner cooking pot. 3) Flip the main unit upside down over a trash can and use a can of compressed air to blow out the vents and the heating element chamber. You'll be surprised at what comes out.
IF THAT DIDN'T WORK If it still trips, the thermal fuse or sensor might be damaged from repeated overheating. You'll need to contact Cosori.
HEADS UP Never cover the vents on the top or back during use. Give it at least 5 inches of clearance on all sides.