I've experienced a Problem I couldn't find any solution for so I write this post here.
My Problem: My friend runs a Modern Skyblock 2 Server and everytime I tried to join I get the message: Connection Lost
Or I get this message: Internal Exception: io.netty.handler.codec.EncoderException: java.io.IOException: Can't serialize unregistered packet
Ingame-message in the picture!
Often I get the "Disconnected" Message and the other error message is out of the log and is a bit uncommon.
What I tried: I tried disabling my Firewall, but when I disable it nothing changed.
We also tried reloading the Modpack and the World and it didn't helped as well.
I tried to play the server world in Singleplayer wich worked fine, I didn't get any Problems there.