No lights or anything turn on? It's plugged into a working outlet? (If it's a power strip make sure it's switched on). Try pressing the button on the front. If it's in auto mode it may not seem to be working, some reviews of it I've seen it takes a lot of vapor to activate it and almost has to be blown right onto the device. Saw several tests of it not activating in a small room even when it was foggy. If none of the lights or anything are coming on when it's plugged in you may need to return it for warranty replacement. Could be a defective unit.