Check if it is due to that the timer is on 2. When the set temperature is reached, the heater will stop working, and come back on when ambient temperature is lower than the set temperature 3. When the ambient temperature is above 50°C / 122°F, the heater will stop heating and the overheat alarm will be triggered with malfunction code FF on LED display and beeps. Please unplug it from the power source and power it on again when the ambient temperature drops below 50°C / 122°F