DIAGNOSIS The touch interface control board has locked up or lost its connection to the main power board.
FIX Unplug the appliance from the wall outlet. Wait 60 seconds. Plug it back in. This performs a hard reset of the main PCB. The screen should light up and show the standby time. If it does, test the buttons.
IF THAT DIDN'T WORK The flat ribbon cable connecting the touch panel to the main board may be loose. This requires disassembly. Unplug, remove the four screws on the back cover, and check the white ribbon cable connection at both ends.
HEADS UP Never spray cleaner directly onto the touchscreen. Liquid can seep through the edges and short the control board. Wipe it only with a slightly damp cloth.