If you try to import a very large model (many millions of triangles) in 3ds Max with the option "Combine All", it is possible that nothing will show up. However, you will notice that the imported elements are there as:
They show in in the project Explorer as "VIM"
They are detected by the "Polygon Counter"
They can be rendered
This problem arises from a limitation of 3ds Max, where single objects beyond a certain large size cannot be viewed in the viewport.
The best solution to this issue is to delete the element and re-import in in a way where the geometry will be split into more segments. Try to use one on these alternatives.
Combine by Materials
Combine by Category
Combine by Family
If you still have issues or questions, click the message icon at the bottom right of this screen to contact Support for further assistance.