DIAGNOSIS The cooker thinks the lid isn't on correctly. It's almost always because the silicone sealing ring isn't seated perfectly in its groove or the lid's alignment arrows aren't lined up.
FIX Turn the pot off. Pop the sealing ring out, wash it, and make sure it's seated fully back into its groove all the way around—no little twists. Then, put the lid on and turn it clockwise until the arrows on the lid and base align. You'll feel it lock. The 'LID' message should clear.
IF THAT DIDN'T WORK Check the float valve (the little silver pin on the lid). Make sure it's not stuck in the up position. Gently wiggle it to ensure it moves freely up and down.
HEADS UP If you've just washed the lid, make sure the inner side where the ring sits is completely dry. A little water can make the ring slip out of place when you put the lid on.