Here are instructions for how to reset air purifiers
Mill Silent Pro Air purifier (Model: APSILENTPRO)
Turn off device
Turn device on
Within 10 seconds, press and hold [MODE] for 10 seconds. This will perform a hard reset on the device
Mill Silent Pro Compact air purifier (Model: APSILENTCO)
Turn off device
Turn device on
Press and hold Fan speed/Mode button for 20 seconds
Once 20 seconds have passed release button and hard reset will initiate
All icons blinks 3 times.