Can you please paste the exact text that comes from the MUD, that you are trying to match against with this trigger? Copy and paste, not retype. Thanks.
MUSHclient doesn't know it is getting German text, so there is no real reason it shouldn't work, unless you had some obscure characters in the trigger, however "Info:" seems straightforward enough.
You say no triggers are working, have you accidentally disabled all triggers? On the trigger list there is a checkbox : Enable Triggers. Make sure that is ticked.
Also make sure "Enable Trigger Sounds" is checked.
Also, edit the trigger and see if the match count is greater than zero (about half-way down the screen). Maybe it is matching but not finding the sound to play.
Well, enable triggers and triggersounds are checked and the matchcount is zero.
I also used this sound in other muds and there it works without any problems.