BlendFile’s here
Here’s what I know
1.A flat Diffuse shader works just fine, with no textures or anything
2.A flat Glossy shader doesn’t work
3.The mesh was looking just fine in Substance Painter
4.I tested the texture in another object just to make sure it wasn’t the material, it turns out it wasn’t the material
5.Even with the high poly normal maps, it refuses to work 
testing to see if you can reply…
I think it works fine on my computer.
hm…
strange…
The problem sticks regardless I use CPU or GPU
what version of blender do you use?
Black edges like that usually indicate a problem with normals. Black faces are blenders way of displaying normals that it thinks are facing away from the camera.
I suspect you have smooth shading over too large an angle (like trying to smooth shade a cube) or the nodes you have plugged into the normal slots of your material are causing issues - or it could be a combination of both things (your screenshot doesn’t show all of your node group so I can’t be sure).
