GCP LB IAP: Troubleshooting

If getting any of these errors:

URL: GET https://accounts.google.com/o/oauth2/v2/auth
Code: 404. Raw Message:

Error authenticating: Error making API request.

URL: PUT https://vault.attracs.com/v1/auth/gcp/login
Code: 401. Raw Message:

Invalid IAP credentials: empty token

You likely have to enable your user, group or service account to the IAP rule in order to let the requests pas through the Oauth.