A couple of things you can try:
- When you collapse your mesh to an edible poly, run reset x-form
- You do have a basic material on it in ue4? If not, drop the basic wall or something like that on it.
- Do you only have the basic lighting setup now? In other words, just the exterior light source? If so, you can drop a skylight into the scene, and even add a reflection capture and a point light with low values inside the room.
- What UVW vert snap thing are you thinking about?