DIAGNOSIS The three-beep red-light alarm means the filter cover is not properly secured or the filter is incorrectly seated.
FIX Power off the unit. Remove and then firmly reinstall the filter, ensuring the alignment arrows match and it's seated flat. Press down on the center of the filter. Replace the cover, making sure all four latches click securely into place.
IF THAT DIDN'T WORK The filter may have been installed without removing its original plastic wrap. Power off, remove the filter, peel off any remaining plastic film, and reinstall.
HEADS UP The unit won't operate with this error, so don't just unplug it and plug it back in—you must physically reseat the filter and cover.