DIAGNOSIS 'CL' is the Clean Filter indicator. It's not based on time since you cleaned it; it's based on total runtime hours. The unit has an internal timer that triggers this reminder after a set number of operating hours, regardless of actual filter condition.
FIX To reset the 'CL' alert, you need to manually reset the timer. With the unit plugged in and turned off, press and hold the 'Timer' button on the control panel for 5-8 seconds. You should see the 'CL' icon disappear from the display. Turn it back on, and it should operate normally.
IF THAT DIDN'T WORK If holding the Timer button doesn't clear it, try unplugging the unit for a full 5 minutes to let the control board fully power down, then plug it back in and try the button hold again.
HEADS UP This is just a dumb timer reminder. It doesn't actually sense a dirty filter. You can reset it even if the filter is dirty, but that'll just hurt performance and efficiency. It's a good nudge, but you're the real judge of when it needs cleaning.