If you keep experiencing this problem, you are always ending up in the backup lobby.
For the most popular lobbies (C&K, basic, toulouse) we have a backup lobby. We use this lobby in case the primary lobby crashes and to easily be able to transfer in case of updates. So, at each moment, there will be a lobby that is currently used (full of players) and one for backup (probably empty).
What happens is, you are unable to connect the primary lobby, the game tries again for the backup lobby, which succeeds. Now you end up alone in the backup lobby.
The most common cause for this problem is a firewall or router problem with the lobby's current primary port: Connecting to the server.