Sketch or filling face can’t be extruded

Like another post on here, I’ve imported a DWG file.
As you can see in the video, I am able to extrude it right after import.

I am trying to do a -2mm offset so I can set a perimeter face. I am able to create the offset, but now I cannot extrude either of the faces.

Now, I was able to extrude it, then do a shell with a wall of 2mm and I think it got me what I wanted.
Just seems like a backwards way to do it.