That's interesting Dan. I have no idea why some parts do not come in. (Actually, Simulation knows there are 6 parts during the import, but only brings in the 3 like you show.) I will check with our developers to see if they can find the cause of the problem.
It looks like the model is not a native Inventor model. Do you know what software was used to create it? Ideally, it will be a package that Simulation can open directly and therefore bypass any other issues.
If not, I used Fusion to open the Inventor assembly, and then transferred the Fusion model to Simulation. Just remove the dummy .txt extension, and then you can open the archive (.ach) with Simulation.
John Holtz, P.E. Global Product Support
Autodesk, Inc. If not provided, indicate the version of Inventor Nastran you are using.If the issue is related to a model, attach the model! See What files to provide when the model is needed.