A search of the forum is always a good place to start. This has been covered many times.
First, check your 3D Projection Settings, make sure the camera is positioned to look at your building, and that the camera height and target height are reasonable. If you can't see where the camera is in the small plan preview, shift-click to place a new camera, Ctrl/Cmd-click to place target.
If that does not work you could try placing a camera in Plan view, select the camera then go to 3D window.
Rubia Torres
