Press and hold the filter reset button for 10 seconds. The flashing indicator should turn off.
If that didn't work, confirm the filter is a genuine PuroAir HEPA 14 filter and is installed correctly with the white side facing outward. The plastic packaging must be completely removed. Only genuine filters will reset properly; alternatives can cause operational issues.
The filter replacement indicator illuminates or flashes based on runtime. It is not based on physical inspection.