It means your imported .stp file is not completely enclosed.
Change to wireframe display to see if the missing surfaces are easily identified. If they're not obvious, use the Find tool to locate single edged surfaces. Once you find them, you'll have to fix up the gap, either through the import data doctor or, as is most often the case in my experience, manually adding missing surfaces.
In Reply to JD Mather:
I have two files that I saved out of another CAD program as *.stp files.
I open in Creo Parametric 2.0 and then enter the Simulation Application to set up a static FEA analysis.
One I get errors and on that same one when I go to set the fixed constraint (Displacement) rotation is enabled by default while on the part that I do not get error rotation is grayed out by default.
Right click on the Import Feature in the browser and Info>Feature and the one that doesn't work reports Make Solid - Make Solid DIsabled while on the one that did work showes Make Solid Enabled.
I did not create or import these files any differently.
How do I Enable Make Solid on the one that is not working and what is an easy way to tell whether you have solid or surface bodies in Creo?
