I had the same problem. Looked up the manual online. Red light indicates water level is low I had just refilled the tank so that was not the problem but manual said to make sure water tank was firmly, securely seated on base. I unplugged the unit, unscrewed the plug on the tank and screwed it back on and then made sure the tank was securely seated on the base, plugged it in and it started working. If the tank is full you may just have to make sure the tank is fitting properly in the base.