Can someone tell me what has happened to the world
crash-2024-01-23_23.38.42-server.txt

After reviewing the crash log itself, it looks like your client is unable to read this config file: "jumbofurnace-server.toml" which is odd as that could mean it may not have access to do so OR something was corrupt during the first install of this update or even the modpack itself. Did you by any chance update from a previous version? Have you also attempted to do a clean install? Is this world from a previous version as well?