How to fill a hole in object

(rank beginner here so assume no intelligence on my part)

Trying to fill a hole left when I bisected a section off the top of this object. Tried at length to no avail so time to ask for help.

thanks

You might want to explain how this does not work because you can:

  • select the margin and press F
  • select the margin and press X → dissolve vertices
  • select the margin and press X → collapse edges and verices
  • select the margin and press M → merge at center

Guessing the mesh is either a 3d scan or was created by AI?

What have you tried so far?

I would suggest trying what @Okidoki suggested, since in most cases that can sole the issue. If for some reason that doesn’t work, I would suggest a link to your file.

Main section shown was done with AI. Have tried clean up->fill holes, and creating a thin flat plane and trying to merge it into that space. Most of my exoerience has been with software for CNC carving, but I’m new to Blender and trying to struggle through.