Heya Paulinus,
I have exact the same symptoms, since the troubles last night i keep connection refused and no populated room list, so it is impossibe for me to play.
Did all the tests (inluding that Powershell script) everything was fine and dandy according to those tests.
MissD gave me valuable information with trying a VPN though,so i connected via a German VPN and bingo: problems were over!
When i switched back to my local IP or to a Dutch VPN, problems started again.
Its not a solution, i know, because gaming through a VPN is not very stable, let alone not everybody has a VPN service.
Are you connecting from the Netherlands by the way? Just curious.
And maybe it helps us to find the cause of the problem.