Unable to show materials on custom models

Hello,

This is going to be a very noob question. I am probably missing a concept.

So I have a room, created by very thin boxes:

I play changing the materials that are already provided by the engine, all ok. Then I try to model(blender) a ship-like door, export the mdl file and the materials are not showing as expected . As you can see the front wall is full grey while the materials in side walls are correctly showing the stone material. I have to point that some of the faces of the object looks to render the material.

In my research I understood that I would need to take care of the UV mapping and the normals of the faces, which I think I did:

What else am I also missing?

Did you enable exporting of UVs (and tangents if you’ll be using a normal map) in the export options?
Are you using the Blender add-on to export your model, btw?

Yes I am using this plugin. But as you said all problem was a single checkbox… Thanks a lot @Modanung !