The Print Studio might be part of an offer that expired, but this shouldn't happen. However, I encountered the same issue with Epson as well. It was advertised that an application would be available, but when I went to the page, a 404 error was provided instead.
You should contact HP and they will give you an exact response regarding the status of the offer: http://www8.hp.com/us/en/contact-hp/contact.html
