Typically this is caused by the coordinate values in the source shapefile being outside the extents of your model or the extents of the coordinate system. For example if you used the wrong UTM zone when setting up you C3D/GIS workspace, then your data may be a long way from your model. Try looking at your source workspace and checking your coordinate system is correct. You can also drag and drop shapefiles into Google Earth to see if it sits in the correct location.
It's difficult to tell you precisely what's going on without looking at the shapefile and the model extents.
Cheers,
Steve
