The first step is to have a look at these common troubleshooting steps. 

Generally, they will resolve the most common problems and save the trouble of a warranty claim. 

1. Check the airflow setting is not set to minimum
2. Check the device has adequate water 
3. Check the humidity level of the room is not over 70%
4. Clean dust off the back of the unit to increase airflow
5. Check the cartridge - does it need replacing? They note that the cartridges need to be replaced every 3-6months

6. If the fan is not running check if the cover is positioned correctly. The fan has a child protection setting so that it will not run if the cover is open

7. Check your USB port or charger is working

Evapolar also has a comprehensive help center on this link here: 

https://support.evapolar.com/hc/en-us