it looks like your normals could be locked! Select polygons in the select menu. Go to normals>unlock normals. Then set to face. You may need to do a soft edge also. See how that goes. Didn't work unfortunately, here's the result after a set to face, if it sheds any more light on anything: Tried inverting the green channel on the normal map in photoshop as well, didn't help either. I tried a render with a light pointing at it and it stayed dark. It's a weird one :/