The Nginx Stats page does not provide so much information as HAProxy. It can be useful only for getting basic statics. But Checker and Autostart services use the Stats page for checking Nginx service status. If you use Checker and Autostart services, the Nginx Stats page must be configured
If Nginx service has not been installed via Roxy-WI, Nginx Stats pag should be checked. If the "listen stats" exists, you should configure Roxy-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 not been installed via Roxy-WI, should be HAProxy Stats page should be checked. If the "server stats" does not exist, you should configure Nginx service for working with Roxy-WI.
The detailed instruction can be found here