I think the games server list is having difficulties at the moment. If you want people from the public to join, they might not be able to.

If it's friends/family you want to join, the solution for now is

Option 1; Go into your steam window on windows, click "view" in the top left, and in the drop down window click servers. Click 'Favourites', and manually add the server. You'll have to join from this list each time.

Option 2; If someone is already on the server, you can right click them on your steam friends list, and click join.

So far that's the round-about way to get in the servers