Probably your model have parts that are very long distance from each other. After opening file BIM Vision tries fit the model in the 3D view – camera must go so far to view all elements and they become to small and invisible from that position. Range of selected elements is shown in right side of status bar. Keep in the mind “Regenerate geometry” option while viewing that files. Other possibility is that model has incorrect units and is extremely large, or some parts has no geometry. If that not helps you, please send to us IFC file (firstname.lastname@example.org).