I have used the documentation to setup testing credentials for the Goolge OAuth2 API and I keep on getting the same error when I try to sign in:
Access blocked: Authorization Error
You can’t sign in to this app because it doesn’t comply with Google’s OAuth 2.0 policy for keeping apps secure.
You can let the app developer know that this app doesn’t comply with one or more Google validation rules.
Learn more about this error
If you are a developer of Chrome backend test, see error details.
I looked up the error and found the following “possible” solution
The current recommendation from google is to move to use localhost/loopback redirects as recommended here: instructions-oob or use the OAuth for devices flow if you are using non-sensitive scopes and need a headless solution.
I am not sure if this is the solution. However, any help here would be greatly appreciated