It could be that the story violated some platform policies or it's temporarily being updated and not accessible. Another possibility is that it's part of a limited-time release and the availability period has ended.
It might be that the story is temporarily down for maintenance or updates. Sometimes, there can also be issues with licensing or permissions that make it unavailable for the moment.
It could be that the story has been removed for violating certain platform policies or because of legal complications. Or perhaps there's a problem with the website's servers and data.