Error "A notebook already exists at that URL" while not existing.

When I tried to set a custom URL, say “xyz”, for my notebook, I got an error “A notebook already exists at that URL.” even though I am not using that URL actually. In fact, I accessed the URL and see the error “You either don’t have permission to view this notebook, or it doesn’t exist.” So, yes, it does not exist indeed. It would be nice to know is there anyone else who experienced the same phenomenon or how I can solve this problem.

Are you making the notebook inside a team? If so, someone else could’ve made a notebook with that URL that you’re not able to access, and you’d see that error page at the URL.

Is it possible that you previously trashed a notebook with that URL? When you delete a notebook, it doesn’t release its URL back into the pool of available URLs, and if it’s been more than 30 days since you deleted it, you’d see that error page at the URL.

Otherwise it sounds like it could be a bug! Feel free to DM me details of your specific situation and I can look into it.

Thank you so much, @tophtucker, for your quick and kind comment.
My notebook is private; I believe the URL is only available for me.

As for the deletion of the notebook with a custom URL, your comment is very informative to me.
But honestly speaking, I’m not perfectly sure whether I deleted the notebook with that URL more than 30 days ago.
I, however, believe I did not do it because I recently recognized this custom URL function.

I apologize if it is true that I DID; I’ll send you DM about my specific situation. Thanks!!