The problem I'm asking for help with is the display (or lack thereof) of the walls for the second floor of the addition.
As I said previously, I can define the room over the 1st floor of the addition, but the walls do not display on the 3D view. So, Eric, what you see is, in fact, the problem. The 2nd floor walls are defined on the plan, but do not display on the 3D view.