Your outer wall hasn’t any outside, just the inside.
And all your faces are reversed (back to front) - you should see the white faces on the insides of the rooms, not the insides of the walls.
To fix that, Select All (shortcut Ctrl+a or on Mac, Command + a), then right click and select Reverse Faces.
How did you draw your walls? The easiest way is usually to draw over the wallls of the plan with the Rectangle tool, then when you have a part of it done, say a whole room, delete the short ends of rectangles where they join or overlap, so you get one face for all the walls of a room. Then use the PushPull tool to pull the faces up to the height of the walls (type the height to get it exact). Select all that you have just drawn with a triple click, and make it into a Component (either R-click, Make Component, or press the keyboard letter g). Give the component a name, then move on to the next room.
Or you can draw two rectangles for a room - one for the outside, and one for the inside - and then delete the inside face.
Since none of your walls have any thickness, or tops, that can’t be how you did it. How did you draw them?
It might be quicker to delete all the vertical elements and start again by completing the rectangles on the ground plane.
I’ve started that process for you in the attached file (compressed to fit inside 3MB).
SKUP_Testv2 JMcC.skp.zip (828.5 KB)
Hope that may help, and not just add to your frustrations.