Does a SolidWorks Simulation (Static Analysis) on a sheet metal part need to be converted first to a STEP file?

I have been able to run a Simulation (Static Analysis) on a sheet metal part by first saving it as a STEP file, loading the STEP file, and then running the Simulation on the converted model. When I try to use the sheet metal part directly, the mesh becomes a flat surface and the simulation fails or gives erroneous results.