For S-4: The official servers, or at least Training Server 1, is not loading a default mission file. This means anyone trying to connect will be stuck on the splash screen.
For everyone: The issue can be circumvented by logging in as admin and typing in the command to go to the mission selection screen, then selecting a mission to load.
For everyone: The issue can be circumvented by logging in as admin and typing in the command to go to the mission selection screen, then selecting a mission to load.