There are a couple of leader texts that have encountered the singular text bug and flown off to Mars. That might be affecting your ability to place geometry accurately, as it affects the range of values SketchUp is trying to handle within finite precision. They also cause zoom extents to make the model seem to vanish. The bug was fixed recently, so I suspect you started this model in an earlier version of SU?
Here’s a version with these texts erased and also the axes reset per @Box observation.
Building Rev5.skp (11.1 MB)
Regarding the plain box version of the house, Solid Inspector 2 says there are stray edges, surface borders, and internal face edges. Examining them, it appears that they are all from situations where two edges are very close to each other but not the same. They border adjacent faces but leave a very tiny gap between them, which is why the group isn’t seen as a solid. I’m finding them very difficult to correct. Perhaps you should do the group over with those texts eliminated and see if that avoids your issues with precision.
Edit: you also have some edges and faces tagged. That isn’t the source of the problem here, but it is a practice that can lead to confusing issues in a model. Edges and faces should be drawn and left untagged.