
If the file you are trying to import is actually just 3D geometry and not related to architecture, choose the None option under Geometry Mapping. However, SketchUp import is intended for architectural geometry. Using the Import DXF/DWG command rather than the Import SketchUp command to import polygonal geometry is recommended.

After importing a Sketchup file into a new blank document, you may see nothing but a blank page. Go to Edit > Select All, then View > Zoom > Fit to Objects. This will focus on the imported Sketchup objects.
If after doing these steps you end up with a blank file containing no objects, make sure you were not attempting to import a Sketchup 8 document. To import such a file, you would have to open it in Sketchup 8 and File > Save As, then choose to save it as a Sketchup 7 or earlier file before importing it into Vectorworks.