Sites are not working on Multisite Network

I've created Multisite Network on my existing WordPress installation. Everything seems fine and I can create sites using Multisite Network, but those websites are not working. I've crossed check htaccess and wildcard isssue and everything looks fine. Like no website exist with this name. I'd an established website and I moved it to Multisite Network. An example site is demo.websitename.com. I have even installed and network activated Pro Sites plugin.

Please also guide how can I let people create their websites on our Network like Wordpress.com using Pro Sites plugin. I didn't find any tutorial on forum. We want our clients to create their websites for free from our website.