Board Thread:Questions and Answers/@comment-72.148.218.208-20161103013957/@comment-212.139.85.100-20171222232259

You need to add this https://minecraft.curseforge.com/projects/vanilla-nei-fix/files to the core mods folder. Something to do with NEI wanting the minecraft.jar file to be called exactly "minecraft.jar" whereas the modpack changes the name to something like forge123xyz.jar. Took me hours of forum surfing to find!