How to reproduce:
1. Open the attached project
2. Make sure that you are using DX11 (Edit->Project Settings-> Player-> Other Settings-> Graphics API)
3. Open and play DemoSceneCanvas scene
4. Notice that material doesn't render

If you switch DX11 to DX9 and play the scene again, notice that it renders

By Design: The UI system only uses the x and y UV values so the z,w are never passed over. This is a memory consideration the UI team took, the same limitation also applies to the UV 0 channel.
User created feature request: https://feedback.unity3d.com/suggestions/please-provide-an-option-to-enable-z-and-w-uv-coordinates-for-uv-channels-in-unity-ui