DIAGNOSIS The touch control panel has locked up or lost power. This is a soft electronic glitch, not a main power failure.
FIX Perform a hard reset. Unplug the power cord from the BACK of the purifier unit (not just from the wall outlet). Wait 60 seconds, then plug it firmly back into the unit. The display should reboot and show the standby screen.
IF THAT DIDN'T WORK Check the power adapter connection. Ensure the DC plug is fully and securely inserted into the port on the back of the purifier. A loose connection here provides enough power for the fan but not for the logic board and display.
HEADS UP Avoid using the unit with a smart plug that cycles power on/off frequently. The sudden power interruptions can corrupt the display's firmware over time. Use the unit's own power button or app for control.