If you open a Power ProStructures DGN file in Navisworks none of the ProStructures elements are visible. To be able to use the Power ProStructures model in Navisworks you need to convert a copy of your model to a Native Solid Drawing model.
First make a copy of your dgn file and proceed working with the copy. (Note that it is important that you use a copy because the ProStructures objects are converted to solid objects.)
For ProStructures Dgn files use from menu “Create Native solid drawing”:
Use the following options
Note that this dialog is from a future version of ProStructures. The SS7 version you will get popups for each of the settings.
Choose all of the parts.
Open this DGN file in Navisworks and the parts are visible.