Check the airflow direction setting. If it's set to the back, you get purification without cool airflow from the front. It's working, but you won't feel a breeze.
Press the airflow direction button on the remote or unit to switch the airflow to the front for cooling.
If that didn't work, it could be in Auto mode and has paused. The sensors pause the fan once target air quality is reached. It'll switch back on when air quality drops. You can press the Standby ON/OFF button to reactivate it manually.
Also, a severe internal blockage will stop airflow. Unplug the unit and check the air inlet holes on the filter shrouds and inside the loop amplifier for obstructions.