When Evolution responds with a "Forbidden", "unable to connect to 'calendar'" or "cannot open calendar: unexpected http status code 405" rejection, while trying to access a Google calendar, this is what you should do to fix it:

• First remove or disable UOA integration.
• Then use caldav method instead of Google (Or right click on primary calendar & select properties).
• In the URL field, set it to something like:

https://www.google.com/calendar/dav/YOURUSERNAME@gmail.com/events
• Use your full user name for both username & email. Then click on find calendars. Enter your password.
• Select the desired calendar & click apply. It will appear in evolution.
• Repeat above steps for other calendars.

DONE!