We noticed you marked this as resolved. This is great you got it fixed hopefully. Feel free to add the fix for other community members to understand how to fix it as well in the future.
For the community, without knowing exactly the step this error is occurring, we suspect one of two potential reasons this type of permissions error might occur.
1. The Client Secret may not have been generated correctly, we’d recommend reviewing our video:https://www.bizswoop.com/wp/googlecloudprintapi/ on the setup and verify the steps. Google API may have generated the secret prior to the redirect URI being registered in the dashboard.
2. During the oAuth, you need to login to the Google account used for the API account and GCP account. If you use multiple Google accounts logged in, this might cause a permission issue. We’d recommend logging out of all Google accounts, except the account used for the API account and GCP account.
I hope that helps anyone else that views the post.
