DIAGNOSIS This usually points to a control board lock-up or a faulty keypad. The main board gets power (hence the light), but the signals from the buttons aren't being registered.
FIX Start with a full hard reset. 1) Unplug the ice maker from the wall outlet. 2) Also, remove the water reservoir. 3) Let it sit, completely powerless, for a full 5 minutes. This allows any residual charge in the capacitors to drain and can clear a software glitch. 4) While it's unplugged, press and hold the power button for 10 seconds to discharge any static. 5) Plug the unit back in (without the tank first), and see if the power light comes on solid. Then reinstall the water tank and try the controls.
IF THAT DIDN'T WORK If only the power light works and buttons remain dead after the reset, the membrane keypad itself might have failed or become disconnected. This requires opening the unit to check connections, which voids warranty. If it's still under warranty, this is the time to contact support.
HEADS UP Before you call it dead, double-check that the lid is perfectly closed. Some models have a safety switch that disables all functions if the lid is even slightly ajar. Press down on the center of the lid to make sure it's latched.