The game servers weren't down. Graal doesn't just have servers for the games, they also have servers handling other duties. The server that authenticates your account was down, therefor it wouldn't let you log in since it couldn't verify your account. There is also the listserver which sends you the list of servers and handles cross-server communication. Listserver isn't important for the mobile servers though since you don't need to pick a server, therefor don't need to connect to it.