I can't see materialized object in HTML

I am going to show a 3d object and it consists of html, obj, mtl and texture files.
3dshow is the project folder and it includes index.html.

And one mtl file is

But I think it didn’t include png file.
The object appears but it has not materialized.
How can I fix it?
I run npm http-server on my local.

You’ll need to share more information to reproduce the problem, the screenshots are likely not enough. What is that JSON? How did you create it? Can you share any of the files you’re asking us to debug?