Diagnosis
A blinking Clean light is this dishwasher's way of telling you the door latch isn't engaging properly. The control needs to see that the door is securely closed and latched before it will allow a cycle to start.
How to Fix It
Open and firmly re-close the door. Listen for a distinct 'click'. If you don't hear it, inspect the latch mechanism on the door itself and the strike plate on the tub frame. Make sure there's no obstruction (like a utensil or bit of plastic) and that the little plastic hook isn't broken. You can also try pressing firmly on the door handle while you press Start to ensure full engagement.
If That Didn't Work
The door switch assembly might have failed. It's a common wear part. On this model, it's integrated into the latch. If the hook looks fine but the machine never sees the door as closed, the switch inside the latch is probably bad and needs replacement.
Heads Up
Sometimes the problem isn't the latch, but the control board getting a false signal. Before you order a new latch, try unplugging the dishwasher or flipping the breaker for 5 minutes to reset the control. It can clear a temporary glitch.