TacoShank’s solution is also useful when you have a project, like mine, that was dragged forward since UE 4.8 with all those changes epic made to the build system and you r project is now in a dirty state. Visual Assist will also complain that it can’t find the UE identifiers etc.
If you’re having trouble following the video tutorial with the copy/past thing, you can also create a new project in the latest Unreal version, and simply copy the content of that field in the nmake section to the clipboardand then paste it in your project.