An access point, switch or USG can be reset via the UniFi App. The device will need to be Online/Connected in order for it to be factory reset via the App.
When you are on the devices page within the App, click on the device you would like to reset > Configure > Forget.
**PLEASE NOTE** Whenever a device is forgotten from the controller, all history and configuration of the device will be forgotten. If you are experiencing issues with a device, please do not factory reset the unit unless stated otherwise by a UniFiCloud engineer.