Q&A for How to Change the Default WiFi Network on a Mac

If you have unlocked the lock, then it probably means that you haven't activated any changes and there is no update to apply. To confirm this, you may want to switch to a different network and apply that one, confirming that the apply works. Then switch back to the network that you want again.

Unfortunately, you cannot. 'Factory settings' by definition involves losing data, as it is resetting your phone to the state that it was in when it came from the factory before any data was on it.

Go to 'System Preferences' and then to 'Network.' Click the lock at the bottom left, and enter the password. In the menu on the left, select the 'Wi-Fi' option, then click the minus sign at the bottom of the list. To re-enable WiFi, click the plus icon next to the minus. In the drop-down menu, select 'Wi-Fi.' Click 'Create.' If needed, authenticate with your Wi-Fi network.

It most likely means that your WiFi has been set as private VPN, which requires administrator status to gain access.