403 Forbidden message when calling the v3 Google Calendar API using a Service Account via OAuth 2.0

Question

This is a follow on from my thread about a 401 error when using the Google Calendar API and OAuth2, which can be found here

This contains details of the account setu

Answer 1

In my case I had to enable the CalDAV API in the Google API console. It gives a 403 response if disabled.

I know this is an old question, but this might be helpful for someone.