Power is on, but won't cook
First, be sure the child lock is off. It may have an "L" or the word "LOCKED" showing in the display.
You can unlock it by pressing and holding the CLEAR pad for 5 seconds or so. Your model may use a different key, maybe the "0" (zero) key.
If that doesn't fix it, since it's still under warranty you should grab your sales receipt and your owner's manual and call LG / Goldstar customer service at 1-800-243-0000 to find the nearest authorized servicer.
There may be some foreign substance on the circuit board or inside the layers of the keypad. Most commonly this is due to spray cleaner being sprayed directly onto the keypad.
Cleaner should be always sprayed on a soft cloth first, then use the cloth to wipe the keypad clean.
Always use alcohol-based cleaner on microwaves, never ammonia-based cleaner, which can crack and/or warp the plastic.
If this is what has happened, it would not be covered under warranty, and it may or may not be repairable.
A handy person can remove the control panel frame and see if there's any liquid inside on or behind the panel.
If so, it is possible to dry it out with an air compressor or heat, but often that does not work.
on Feb 20, 2011