I'm not sure what the screenshot is showing. If you're referring to the players in the hub, it could be caused by a restart or crash. If it's a crash it'll be fixed as soon as possible.
Oddly enough, a few other of the servers (factions, skyblock) are not up. May be a main server-wide glitch?
Actually, we're aware of these problems and are working hard to resolve them. I apologize for the inconvenience.