Hi, and welcome to AFF!
One of the things that's been going on, if you check back on some of the Site News threads, is that we're in the midst of a code rewrite. A great many features are being revamped, but the new code is being rolled out in stages so that we can troubleshoot it as we go, without risking a crash of the entire site.
In the meantime, the archive search feature does work reasonably well. You need to begin in the subdomain you wish to search, and keep in mind that words or tags of three letters or less do not work. I find checking the box to allow the MySQL boolean search mode helps a great deal.
Alternatively, many subdomains are broken down into categories and subcategories, which can allow you to refine your search by a type of pairing, such as M/M, or by a specific ship, such as Harry/Draco.
And finally, if you're looking for something a little less specific, you can always peek in the Searching for a Fic threads here in the forum. It's always possible that someone had been looking for similar types of stories, and you can find recommendations and links to stories that way.
As we roll out new features, we will publish updated announcements in both the archive and in the forums, so stay tuned.