The other issue is that while our administrator, DemonGoddess061, is reviewing each subdomain and dealing with leftover issues from the past, she also has a great deal else on her plate, including real life.
Harry Potter has not been cleaned yet. When it's cleaned, empty pairings created before we had a clear policy, or where the stories were removed by the authors, will be eliminated. As JayDee said, we require at least 5 existing stories for any pairing category now, although in the past that was not done.
If you can list five or more stories for the pairing you want to see, by all means create a category request post following the instructions in that thread. Just keep in mind that DG doesn't have the time right now to clean up the Harry Potter subdomain, particularly since there are other subdomains ahead of it in the queue.
Thanks for your patience!