@sean Go to “console.cloud.google.com”, then to “Api and Services”, select your project, then “Credentials”, then “OAuth Consent Screen”, indicate your E-mail address, try again "node auth_and_test.js "and tell us!

Here are the steps you must do before asking for authorization;
https://developers.google.com/assistant/sdk/guides/library/python/embed/config-dev-project-and-account

Specifically in;
Configure the Developer Project and Account Settings and Register the Device Model.
Luck! Come back with your feedback!