I'm currently having this issue. When I attempt to connect to the German server it comes back with "Unable to connect to server. Server is probably offline." When I attempt to connect to the U.S. server it comes back with "Unable to connect to server, check your internet connection." My internet connection is obviously fine, or I wouldn't be able to post this.
I haven't been able to connect to .de since the server went down for maintenance, I was able to connect to .us after maintenance, but when I attempted to join a modern match it gave me an error stating that the version of
Baral, Chief of Compliance I was using was not supported on the server or some such, and when I attempted to create a sealed tourney someone joined and I was able to start, but there were no cards.