Problem with prefab display. tiled2unity issue or Unity or Windows 10?

Prefab is white, why?

This should be a problem with your materials not being exported properly. Have you checked if the materials used for that object aren’t white? If so, try re-exporting from Tiled. It’s definitely not a problem with Windows 10

What are the objects being displayed here? If the solid white is the prefab then what do you have on the right side?

The first place to look for potential errors is in the Console window in Unity. If there was a problem setting up materials then it should be reported there.