Soften/Harden Edges not working

Can't harden edge

Hi guys,

When I try to harden the model edge but nothing happen.
when I export model to .obj & .fbx and start a new scene/doc and repeats the above and nothing happen when I try to harden the edge.
I wants to get the black shaded parts out of the model. I look at the normal face, it go everywhere.
my main issues is that why can't I harden the edge? and how to fix it.

Thank you so much!

SOLUTION
"First unlock the normals Mesh Display> Unlock normals, then same menu Harden Edges or set Normal angle if you have some round corners"

Sgt_Rock in reply to: PawinC