Mine is also being exceptionally weird, followed all steps, had the same issue as ericisawsum, went into my Json and manually fixed modPaths and it populated correctly. But when I opened my world all modded items ceased to be for whatever reason. Interestingly it seems like mods that just changed values of vanilla stuff (ex. a boost to greenhouse temperature) worked fine but items added just dont exist (ex. Iron Spear, it has been replaced with a black rectangle). What can I do to fix this?