You should be able to simply use soften / harden edges.
If this does not work then you should check to be sure you do not have flipped normals along that edge. This is a common problem especially if surfaces were joined.
If that does not work try mesh > cleanup and check lamina faces, nonmanifold geo, edges with zero length, faces with zero area.
If that does not work than I don't know what else to try.
"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675