Registration problem on subsites

I'm trying to sort out the subsite default redirection to the main site on signup. A member of your staff team recommended "Membership 2 Pro" to achieve the goal. After several attempts of configuration and setting up, the "subsite.MainSite.com/register" has redirected to the wrong non-existent URL "subsite.MainSite.com/privacy-policy" and also giving me "404 Not Found" message. Please find full detailed issue on this thread.