The viewport in any orthographic mode when a mesh have a material that deform it, the mesh is not even in the viewport and if you edit it to have the mesh on the location that should be at select it don’t get the hightlight properly working.
No sorry, got the account space filled. But basically you need to open a projecr or create a new one, place in the world the default box or some mesh, create a new material and add the code from the link screenshot