I'm attempting to create assemblies with imported files found from manufacturer websites that were converted from STEP to part files, and in certain parts flashfit along with other specified functions won't recognize faces, planes, or lines. In fact, all it will recognize are center points of circles. However, some parts in the assembly don't have the same issue, and will mate with each other just fine. Any advice?
Like Ken said, it would be easier to tell if there was an uploaded file to look at. My first guess is that the faces/planes for the imported parts may be surfaces, not true faces/planes and the lines may be curves. One way to check is to use Inquire Element to see what type of geometry is reported.
Assembly relationships such as mates, planar aligns, etc. rely on the faces being true planes, not a planar surface. This also holds true for other commands that require a plane as input. So, when looking for planes, those faces are not responding to the selection request since they are not true planes but are surfaces. Even though the surface looks like a plane, it does not respond to plane requests.
It means the lines are not lines but instead curves. It means the surfaces are not planes but instead curved surfaces (curvature could be zero).