Diagnosis
Total lack of power is almost always a supply issue: a loose power cable, a tripped GFCI outlet, or a faulty power adapter.
How to Fix It
Check the power brick on the cord. The LED on the brick itself should be lit green. If it's not, try a different wall outlet—preferably one not on a GFCI circuit, as these units can trip them. Firmly reconnect the DC plug into the back of the ice maker; it can look connected but not be.
If That Didn't Work
Test the power adapter with a multimeter if you have one. The output should be 12V DC. If the brick's LED is on but no power reaches the unit, the internal DC jack or mainboard fuse is likely blown.
Heads Up
Never use a generic 12V adapter—the polarity and amperage must match exactly. Using a wrong adapter will instantly fry the control board.