Here I provide another possible solution for you. I have checked the normals and clear the history and non deformer, but none of them work. I notice that Blender and Maya both have no problem, but in Unity some of the faces won’t show. So I select the faces that is missing in Maya, then I triangulate them. It seems that the problem is that the faces that is missing in Unity are curved, but there are no edges on the curved poly faces. So I guess Blender and Maya can understand what it is, but Unity can’t.
I tried that too but no success…any suggestions are more than welcome. Its really hard to import every object in the scene from a different maya project…It wont except any change in the scene. it just wont import it in the scene.