You can use our another Google Authenticator plugin which does not require the registration. Here is the link to the plugin: https://wordpress.org/plugins/miniorange-google-authenticator/
This plugin works out of the box on your site and does not involve any third-party services for enabling 2-Factor. It is completely an On-Premise software that enhances the login security of your site by enabling Google Authenticator as the authentication method.
