I believe you need to use @ instead of !, because that's what kbin uses, even though lemmy, that you try to access uses !.
I don't quite understand how is that supposed to work, and looks broken imo. If you're the first person to "look up" a lemmy community this way, it will be created on kbin side, with Ernest as a creator, but nothing else is synchronized from before it was "created", or at least it takes time to do it. It feels really inconsistent.