[Gmsh] STL Mesh generation surfaces with inward normalnot meshed?!

[Zuheyr Alsalihi]

Dear colleagues,

I could not easily describe the problem.

A rectangular slab step file that I have generated, attached CG1.step, shows the top and bottom surfaces inward normal.
I am not able to reverse this.
But the surface is there, see Pic1.png. When I create an STL mesh with GMSH gmsh-4.5.6-Linux64/bin/gmsh
these 2 surfaces are not meshed. Can you please help me understand and solve this problem?
Many thanks for reading.
Kind regards,
Zuheyr
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