This means that the server is under maintenance at the moment. Maintenance used to start at 5:00 a.m. Taiwanese Time, Now it starts at 8:00 a.m. Taiwanese Time (7:01 Central Time) These server maintenance lasts generally 6 hours according to my knowledge and once they are done, you must re-patch the game with the English patch executable. These server maintenance are every Wednesdays at around noon (Thursday in the morning in Taiwan)

So please, Don't post a thread asking about Authentication Error, because this pretty much answers your question. And the Mods don't really appreciate it when people start threads asking the same question