why am I getting 'wifi network requires a WPA2 password?'

It is possible that the password saved on your Mac is not the correct one. to fix easily, Forget that network and any stored password (using EXACTLY the procedure in this article).

When you later try to use it, the network will be "new" and a new password can be entered in the dialog-box that will appear.

How to forget a Wi-Fi network on your iPhone, iPad, iPod touch, or Mac - Apple Support

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Because whatever WiFi network you are trying to join requires a password.