As you can see in the image, i get an Interna Exception when i try to join the server i made. Right after i made the server, i joined it to chekc if it worked, and it worked fine, but my audio in-game was not working, (which happens for me sometimes, i just have to restart the game), so after restarting and trying to join again, i get this error...
The server is the RAD2 modpack (Roguelike Adventures and Dungeons 2)