“Error 403: access_denied” from Google authentication web api despite google account being owner

To fix this issue for me was this simple:

1. Go to https://console.developers.google.com/
2. On the top left beside the words “Google APIs” click the project dropdown on the right
3. Ensure that your correct project is selected
4. Click “OAuth consent screen” on the left side of the screen (below “Credentials”)
5. If you have not created a consent screen, do that first
6. Under “Test users” there is a button called “+ ADD USERS”
7. Type the email of the account you will be testing with, press enter, then click save.
8. It should work now!

It seems like they updated this recently because last year I did not have to do this.