Timeout while connecting to coordinator.openttd.org:3976

[brummbaer76]

Hello,
My server has been losing the connection to the Game Coordinator several times a week. After restarting the server, it immediately reconnected, so the connection is basically back.

But for the past few days, I've been getting these messages right when I start it up:

Timeout while connecting to coordinator.openttd.org:3976
Connection with Game Coordinator lost; reconnecting...

I can't connect at all anymore. What could be causing this? Firewall rules haven't been changed, and no operating system updates have been performed.

Does anyone have any tips?