DIAGNOSIS: Dead batteries in the remote are the first suspect. The second is the unit's infrared sensor being blocked or the remote being out of alignment.
FIX: Replace the remote's batteries (2 AAA). Point the remote directly at the front-panel display on the AC from no more than 10 feet away. Ensure no furniture or objects are blocking the path.
IF THAT DIDN'T WORK: Test the remote on your phone's camera. Point the remote's LED at your phone camera and press a button. If you don't see a purple light flash through the camera viewfinder, the remote is dead and needs replacement (order LG part AKB73675607).
HEADS UP: The IR sensor on the unit is behind the small dark plastic window on the front panel. Keep it clean and free of dust. Sunlight or very bright room lights can sometimes interfere with the IR signal.