Diagnosis
The ice maker's internal shut-off arm (the little plastic feeler) is probably stuck in the 'up' position, which tells the unit the bucket is full even when it's not. This is a super common freeze-up issue.
How to Fix It
1) Unplug the fridge for safety. 2) Remove the ice bucket. 3) Look for the plastic feeler arm. You'll likely see ice jamming it. Gently pour warm (not hot) water over the arm and the area around it to melt the blockage. 4) Manually work the arm up and down until it moves freely. 5) Plug the fridge back in. You should hear the ice maker cycle within a few hours.
If That Didn't Work
If the arm moves freely but it still won't make ice, the water supply might be the culprit. Check that the water filter (located in the top right of the fresh food compartment) isn't clogged or overdue for a change. A clogged filter will stop water from reaching the ice maker entirely.
Heads Up
When you change the water filter, you'll get a big gush of air in the line. Expect the first batch of ice to be hollow or small, and it might take 24 hours to fill the bucket again.