From left to right, the icons in the upper left corner of the purifier represent the pre-filter HEPA filter and the activated carbon odor filter respectively.
If it's red, change it. If they are all red, they have to be replaced. Open the front cover of the machine from the outside to the inside: front filter HEPA filter and activated carbon odor filter.
After the replacement, press the small hole under the indicator lamp with a toothpick or something for 5 seconds, and a beep will appear, and then the reset success signal indicator light will turn green (click the reset hole corresponding to which filter to replace).
I hope it helps. You can leave a message if you have any questions.