Your issue might be related to the permissions of the service account you set up in the Google Cloud Platform console. It could be possible that your service account doesn’t have the proper permissions in Google Analytics to access account data. If you’ve given the service account the necessary permissions temporarily, it might still take some time for permissions to propagate. Make sure that in the Google Analytics Admin settings, under Account User Management, your service account email is listed with “Read & Analyze” permissions at minimum. If the problem insists, you might want to cross-check if the key file is associated with the same account that has been granted the permissions.