When you set up the Google Play: Reply to Reviews Integration, you receive a 400 Error with the following text: "The redirect URI in the request (urn:ietf:wg:oauth:2.0:oob) can only be used by a Client ID for a native application. It is not allowed for the WEB client type. You can create a Client ID for a native application in the Google Developer Console API section."
This error appears when you choose an incorrect app type when creating an OAuth client. Make sure to choose the "Desktop App" application type.