In object mode, my pin has this “seam” that cuts it in half, though it’s not noticeable in most other views.
Are you sure that the line you’re seeing isn’t just the Bezier Curve? I can see from your outliner that you followed the instruction of keeping the actual curve as well as the mesh version when you converted it to a mesh. try clicking the little eye icon next to the curve object in the outliner and see if that gets rid of the “seam” you are seeing.