Diagnosis
The main electronic control board has likely locked up or failed. A power surge or glitch can cause it to freeze, much like a computer.
How to Fix It
First, try a hard reset. Unplug the fridge from the wall for five full minutes. This drains residual power from the board. Plug it back in. Wait another five minutes for it to reboot. Often, the panel will come back to life.
If That Didn't Work
If the panel is still dead or acting crazy, the control board itself (located behind the kickplate at the bottom front) probably needs replacement. The part number is WR55X10942 for many units, but you should verify by pulling the kickplate and checking the sticker on the actual board.
Heads Up
Before replacing the board, check the wiring harness connector that plugs into it. Look for any loose pins or corrosion. A poor connection can mimic a dead board and is a much easier fix.