You weren't the only one experiencing this issue, as seen in this thread on the forums. I cannot go into detail with what Cipsoft was exactly doing but what they said about the downtime (November 19 2020) here and here is that they.."had to take all game worlds and the website offline due to critical technical issues related to yesterday's extensive changes in our backend infrastructure." So either this was done purposely to fix technical issues or this happened by mistake. But when a server is private that means simply it's closed off and only open to only certain people.
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