Mullti-site installation on main site using Builder

I followed this blog post to set up multisite on an existing site.
I used my C-Panel to add the first subdomain and created a site in the Network .
I tried to clone the main site to the new site and also, I tried to visit the URL directly. Each time, I got a 404 error page. I have traced my steps and can't find anything I missed. I enable access in my WPMU dashboard.
I am creating an intranet with client, contractor and employee portals.