Make sure you have installed. While launchers like CurseForge often manage Java versions for you, if you run into issues, you may need to manually install Java 17 or Java 21 (depending on the Minecraft version of the pack).
How to install the game onto PC - Granny: Buttery's Mod Pack - Guides granny buttery mod pack download new pc
: Once downloaded, Steam will provide a file path to the depot. Navigate to that folder. Make sure you have installed