On Win 11 AI 27.9.3 I had a strange problem where when I hit paste and thought I had your issue, but instead it pasted way far outside the artboard. It is supposed to paste in center of artboard, in my 35+ years of using Illustrator.
So I removed the old illustrator and went with AI28.4.1, which at least pasted onto the artboard. How it decided that location Maybe this is a windows 11 issue, what OS & AI version are you using, as this is important?
Let's troubleshoot your issue. Can you try to confirm if the copy is indeed happening? After you paste do a select all and you can see the bonding box, and if it goes out farther. Also check it is not doing a paste in front by selecting the object and deleting temporarily so one is not underneath.
Next try a paste in front, to see if the copy worked.
I find it strange that if you do a copy, it does not say undo copy, but it will show in undo for paste.
Until we figure this out, try alt dragging to create a copy for some relief.
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