Cant join or sweep this naked edge:/

Here is the ring, the screen shot shows the naked edge. I’ve tried merge, sweep, join, etc and am not sure what to do next. Can anyone on here advise?
DB10 rhino.3dm (1.1 MB)

Zoom in close and you’ll see the mess that needs to be cleaned up to fit better.
Explode the surfaces and run RebuildEdge so you can see what you’re dealing with.

I found an extra triangular surface on the front so I deleted it. Then I used MatchSrf to change the top of the remaining triangular surface and matched it to the edges of the top two nearest surfaces.
Then Joined them together into a close polysurface.

DB10 rhino Fixed.3dm (1.1 MB)

Thank you for your help. I am trying to go back and repeat what you did, but as you know a command is never as simple as a command. After using matchsrf I got a weird form which I then erased and filled the space using sweep2, joined edges and now there are no more naked edges.
Much appreciated.