This all depends on the way the APs are deployed:
Reason: The #use enterprise-ui settings is removed from the AP profile once AP is reset and has to be re-configured.
- Standalone APs:
- APs deployed in Standalone mode, will lose access to the GUI once reset back to factory default settings and the Enterprise UI will have to be re-enabled.
- Adopted APs:
Reason: The #use enterprise-ui setting is still configured in the AP profile on the controller so once the AP re-adopts and pulls the config, it will reboot and the Enterprise UI will be automatically re-enabled.
- APs that are adopted by a controller and reset back to factory default settings, will have their Enterprise UIs re-enabled automatically once they are re-adopted. An automatic reboot of the APs will have to be taken into account when considering downtime.