This question is an exact duplicate of:
Recently I casted a Close vote on this post How to disable sort in DataGridView? as a dupe of this post Best way to disable the column header sorting in DataGridView.
Later the moderator Cody Gray closed the other one as a dupe of this post.
If it's confusing, let me explain.
I casted a Close vote on A as dupe of B. Then a mod closed B as a dupe of A.
Now I can't retract my close vote.
I tried it after the mod closed the question.
But the close vote count changed from 1 to 0. Also The retract button is not there.
I checked it today and saw the same message. I can't retract my Close Vote.
Since the working of Close is same for all SE sites, I don't think this is an issue pertains only to Stack Overflow.