Diagnosis
The ice maker's internal fill cup is frozen over, or the water inlet valve is faulty/clogged. The frozen fill cup is the most common culprit.
How to Fix It
Manually defrost the ice maker assembly.
1. Remove the ice bin. You'll see the ice maker unit on the left side.
2. Unplug the refrigerator. Use a hairdryer on low heat to gently warm the ice maker for 5-10 minutes, focusing on the front where the plastic fill cup is.
3. Alternatively, leave the fridge unplugged with the doors open for a few hours to let it thaw completely.
4. Plug back in. You should hear a reset cycle and then see the fill cup attempt to fill with water.
If That Didn't Work
The water inlet valve (located at the back, bottom of the fridge) may have failed or the water line is kinked/frozen. Check that water is flowing to the fridge by dispensing water from the door. If that's also slow or stopped, the issue is with the water supply or main inlet valve.
Heads Up
If your freezer is set colder than 0°F, it increases the chance of the ice maker freezing up. Set it to 0°F and keep the freezer at least 2/3 full for stable temps.