The server Sh3 disconnected .
It is certain that it is disconnected for some time, the causes can be so many as we want to think: economic, fights among clans, with insults, obsolete considered game etc...
The reality is that it doesn't work and we don't have a clear answer from Ubi.
I play on line Sh3, Sh4, and Sh5 in Silent Hunter, and also Il2 Sturmovik, but with Hamachi and lately with Tunngle, Ubisoft should give explanations when it disconnects a server that has always been active.
The only clear answer I can give you is that the servers have been discontinued.
My best guess is that there were not enough users to necessitate keeping the servers active.
It's unfortunate for you die-hard fans, but I hope you have good luck with those 3rd-party hosts.
Thank you for their answer, it is a pain that the games of Silent Hunter don't have the attention that deserves, anyway the fans as me we will continue playing in a way or another.