Unity 2017 missing prefab

After updating to Unity 2017, my level geometry is gone and is now a missing prefab placeholder. Why is this? The level model is still there, so I can’t tell what happened.

Hi, guys! I got same problem with lot of “missing prefabs” and glitchy scenes after updating project to Unity 2017. In my case problem was with Blender - I didn’t have it installed so Unity couldn’t update any of meshes. I have installed Blender, tried to update on 2017 version again and everything went smooth now. Hope that could help you!