The servers have moved to a new IP address. If you're not seeing them in your favorites, that's why.

To find Sodahappy servers, search for servers that have the tag "sodahappy". Here's an image showing how:
http://i.imgur.com/vjZDup0.png

You may need to "Refresh All" after entering the "sodahappy" tag.

You can also get the IP addresses from the official server list:
http://forums.sodahappy.com/threads/8-Sodahappy-TF2-Server-List

After you connect, you can add it to your favorites by clicking the "Add a Server" button at the bottom of the "Favorites" tab.