The heater is equipped with a safety feature that keeps it from getting too hot. If the heater will not turn back on, it could be because that safety feature was activated. Shut the power off, unplug the unit and let it cool down for approximately 30-45 minutes. Take this time to clean your filter. After the unit has cooled down, try plugging it in and turning it back on. If this does not solve the problem, please call Customer Service at 1-888-281-9031.