Rhino for Mac - not picking up the non-manifold edges

I have sent my model for 3D printing and it does not pass because “non manifold” edges are found. With the “showedges” command I could see the naked edges and fixed them but when toggling the non-manifold nothing comes up. I just got a snapshot from the 3D printing folks using Rhino-Windows and they can see them.
What am I doing wrong or someone else has seen this with the mac version? I have the version 6

post the file?

here it is non manifold test.3dm (8.3 MB)