Details
Error Message: "Client is unauthorized to retrieve access tokens using this method, or client not authorized for any of the scopes requested."_
Potential Cause/Resolution: This error generally indicates that your client (application) isn't sufficiently authorized to perform some action in Google Cloud Platform.
Steps to Resolution
Check that "Domain-wide delegation" is enabled for your service account in the Google Cloud Platform console. This is included under Step #9 in the GCP portion of the setup process. For more information, reference this article from Google Cloud Platform's developer documentation
Check that the scopes included in this document are properly entered in the G Suite Admin Console and that those scopes are associated with the Client ID of the service account you created. This is included under Step #4 in the G Suite portion of the setup process.
Ensure that the "Service Account Token Creator" and "Service Account User" IAM roles are assigned to your service account.