DIAGNOSIS That's a classic control board error state. It's usually triggered by a momentary power surge or a glitch during the last use.
FIX You need to perform a hard reset to clear the memory. 1) Unplug the air fryer from the wall outlet. 2) Press and hold the power button down for 15 full seconds. 3) Wait 60 seconds, then plug it back in. This should clear the error and the lights will return to normal.
IF THAT DIDN'T WORK If it's still flashing, the internal fuse might have blown. You'll need to contact Cosori support for a replacement fuse or unit.
HEADS UP Always plug your air fryer directly into a wall outlet, not a power strip, to prevent these voltage-related resets.