The Nginx Stats page provides not so much information as HAProxy, but it can be useful only for getting basic statics. But Checker and Auto start services use the Stats page for checking Nginx service status. If you would like to use Checker and Auto start services the Nginx Stats page must be configured
If Nginx service has been installed not via HAProxy-WI, should be checked Nginx Stats page. If the "listen stats" exists, you should configure HAProxy-WI for working with your configuration.
Go to the Servers -> Settings. Edit settings inside the "Nginx section" according to your server stats configuration(in the black box)
If Nginx service has been installed not via HAProxy-WI, should be checked HAProxy Stats page. If the "server stats" does not exist, you should configure Nginx service for working with HAProxy-WI.
How to do it you may read in this article