Authorization Needed to Access e-Play on Adobe Digital Editions 4.5

I'm trying to access an e-Play I purchased last year but when I login using my Adobe account, it says:

"The vendor account you entered is not associated with the item you are trying to open. Try again."

I only have one account that I've used to purchase e-Plays so I'm confused as to why it won't let me read this play I paid for.