Some sites are not working after activating cloudflare

I just enabled this service to my site. I can't access two of my sub sites now. I get this message.

The server at .... can't be found, because the DNS lookup failed. DNS is the network service that translates a website's name to its Internet address. This error is most often caused by having no connection to the Internet or a misconfigured network. It can also be caused by an unresponsive DNS server or a firewall preventing Google Chrome from accessing the network.

Sites that affected are,

The main site:

Please help!