I've never had the Heal Edges tool actually work. I feel like I must be doing something wrong.

I typically need this after a surface has been extended and now has 2 edges (old edge & extended edge) where there should be one continuous edge.

i.e. the surface below was offset then extended. It should only have 4 edges.

I've tried angular tolerance of 1, 5, 10, 45...

Tried super short edge length tolerances of .01 all the way to 50mm.

It does nothing. What gives?