Why is Google Calendar API (oauth2) responding with 'Insufficient Permission'?

Question

I'm doing a get request to the following URL (with {id} replaced with the id from the web interface):

https://www.googleapis.com/calendar/v3/calendars/{id}

A few assertions:

1. The Authorize header is being correctly set with a valid access token (the token works fine for the Analytics API)

2. I've set the following scope for oauth2, which shows up correctly:

   https://www.googleapis.com/auth/calendar
   

3. The token doesn't appear to have expired; it works for the Analytics API.

   { "error": { "errors": [ { "domain": "global", "reason": "insufficientPermissions", "message": "Insufficient Permission" } ], "code": 403, "message": "Insufficient Permission" } }
   

Answer 1

To fix, I revoked access to the app at https://accounts.google.com/IssuedAuthSubTokens and retried after which, I was able to access the API correctly.

Despite having the scope in the list, and the scope showing up on Google's OAuth2 grant page, the additional scope wasn't granted.