Playing an old downoad?

I downloaded a tunes call St. Louis Blues - Peter Cincotti back in 2004. I've kept the file and when I attempt to play it, it asks my to authorize the computer to play it. SO, I put in my credentials, and it says that I have used 4 out of 5 of my authorized computers, and then proceeds to do nothing and doesn't play. SO I thought, I'll re-download it again. When I look in my purchase history it isn't there. However I DO have my emailed receipt and and it clearly shows that I used the SAME email and user ID that I have now and still using. When I look up that particular tune now, it's called St. Lewis Blues by the same artist.

So how do I get this thing working?