Why is my refill light coming on even though there's water in the tank?

There are a few things to check that would cause the empty light to go on:

• Please rinse the lid on the bottom of the tank. After you rinse it with warm water, dry it and then push the spring on the outside of the lid, it should move easily. Check the inside of the lid and make sure the rubber gasket is securely in place. When twisting the lid onto the tank, please make sure that it is not over-tightened
• On the base of the humidifier to the side of the ultrasonic disk is a small white plastic pole with a washer-ring around it. This is the float, make sure it moves easily up and down the pole. Tap the base of the machine on a hard surface. This will clear any air bubbles inside of the machine should there be any
• Reassemble the humidifier, use room temperature water in the tank and let run for 30-40 minutes. Please make sure the humidifier is on a flat level surface, no carpeting or towel underneath