Could you please provide us with a link to your scene or send us (to support@shapespark.com) a .zip file with the problematic scene?
This way we will be able to investigate this issue faster.
The preview issue is due to the fact that all the ceilings you have there are parts of object switches and they have the option isolate shadows enabled. This means that the ceiling won’t block the light from the sky, this explains why you see the sky instead of the ceiling.
The unnatural shadows are due to this as well, the ceiling doesn’t block the sky and sun light.
To fix these issues you need to have a ceiling that covers the whole floor, so that it blocks the skylight from entering to the scene from above. You can make it invisible by using the “Custom hide in views” option in the objects tab. The ceiling has to have the isolate shadows option disabled, otherwise it wouldn’t block the light in the same way the current ceiling blocks it in your scene. To not waste your time and your machine’s resources on baking of the artificial and invisible ceiling you can also set its custom lightmap resolution to 0. You can use the preview feature to make sure that the new artificial ceiling blocks the skylight.