This issue could happen for a few different reasons:

1. The objects could simply be unloaded (the checkbox in the 3D tree is unchecked) or hidden. To check and fix this, open the 3D Objects window and left click to enable the check box next to the imported file name
   
2.  The objects may be a set of 2D lines rather than 3D objects and the visibility of lines is disabled.
   To fix this, open 3D View Properties>General and check the box for Lines under Visibility
   
   
3. The model objects may be filtered in the BIM file or the file contains only 2D geometry and nothing was imported. Try importing the models with Ignore hidden 3D objects and Ignore wireframe 3D objects unchecked
   
4. It could be that one of the models contains a reference object that is placed very far away from the bulk of the model and is causing bounding box issues.
   To see if this is the case, you can select a leaf level 3D object and then right click in the 3D window and Zoom>Selected Objects.