Google Workspace (formerly GSuite) Authorize App error 400: invalid_request

When attempting to Authorize App on either the Source or Destination tabs, you receive an error 400 which reads (in part):

Error: invalid_request

Invalid parameter value for redirect_uri: Non-public domains not allowed: http://IISservername/unitysync/gsuite.cgi/auth

This error occurs when you have configured your UnitySync User Interface (UI) to be accessible via IIS. Google Workspace connections must be authorized using dirweb.exe instead, as Google Workspace reads your IIS server address as a non-public domain.

To proceed, close the UnitySync UI in your browser, then relaunch using direweb.exe, which is found in …\unitysync\bin. From this instance of the UI, try the Authorize App button again, and your results should be sucessful.

IMPORTANT NOTE: Please note that your Authorization should remain unless your Sync is interrupted, either manually and due to a crash. Your Google Workspace token is written to your configuration on each sync, and without that refresh, your next attempt will fail. Simple reauthorize the app to move forward and, if you are experiencing a crash issue, contact support@dirwiz.com for troubleshooting assistance.