Possible Cause #1:

Air purifier is operating in manual mode

Solution:

Select your desired operating mode 

 

Possible Cause #2:

Air purifier is operating in Haze / Silent mode

Solution:

Air cleaning level cannot be manually selected in haze / silent mode as it will run at its own set level (minimum level in silent mode, maximum level that is higher than "High" in haze mode) 

 

Possible Cause #3:

Room is too dark - air purifier is operating in sleep mode

Solution:

Air cleaning level is set to a minimum during sleep mode

 

Possible Cause #4:

Air purifier is in Quick cleaning mode

Solution:

Air cleaning level is set to maximum during Quick cleaning mode