Sketchup model won't upload with materials

All of a sudden my model uploads without textures. It was fine an hour ago. I tried copying and pasting to a new file, no effect. I have another version of the same model, which uploads fine. Anybody have any idea how to fix this?

What method do you generally use to upload? If I’m not uploading directly from an application such as Substance, I usually upload a ZIP file containing both my model file (.obj, .fbx, .blend) and a subfolder with all required textures. Uploading textures on their own has a tendency to not work properly, in my experience.