HELP! Why do I have a cut there?

Hi! I am a very beginner in Rhino. I migrated a pipe elbow to flatten that via ExactFlat in Rhinoceros. There’s a wide cut on the outer side for reasons but there is nothing on the inner side which could cut the surface (however you can see a line cutting the pipe in half lengthwise).
After file opening, software sees the surface as one (even if line is visible) but when I try to flatten, it shows an error in the mesh, I can only correct is automatically which cuts my surface in two, as in the picture. Could you
please help me? Maybe you can’t with only this much information but maybe you can correct that for me in a few words.
Pic
Thanks in advance!

Your link results in: “Gone Error 410”

If you are still having difficulties try upload a Rhino .3dm file with the geometry. You can use the vertical arrow above where you type your post. I don’t know how many ExactFlat users are available to respond though.

Thanks for your fast reply, yeah, link is only visible for me. :tired_face: Sorry.

Maybe this way. :slight_smile: If it won’t work i will upload 3d file for sure and thanks if anyone is able to help.

Dávid

Looks like it was booleaned with a thin horizontal plate. We’ll need to see the file to help with this.

FYI, the rhino command ScreenCaptureToClipboard will generate a better image of the problem than a photo.