Simplify3D User Forum

I am new to Simplify3D. My first attempt to use Simplify3D failed with corners missing from the sliced model and the print. I am attaching a screen shot of the model and the sliced version. Notice how the corners are all missing in the sliced version of this. Any ideas on how to fix would be appreciated.
This slices properly in Slic3r.

It appears that the STL is comprised of multiple objects. The quickest way to address it is to select "Separate Connected Surfaces" in the Mesh menu. The more involved way is to import the STL into an app like Meshmixer and apply its fixing tools.