Packaging error 5.4.4 Ensure condition failed: Materials.IsValidIndex(Section.MaterialIndex)

Hi, sorry for the delayed response. I did have an issue with a skeletal mesh, but it wasn’t being used in the project. Check the errors you get when you launch the project, or by doing a cook. I spotted it through one of these two methods. This will help you identify it. As for resolving it, I simply deleted it.