I do not know why your keycode should not work anymore, unless it has been revoked (credit card charge back or similar)
I am not 100% sure about any credit card charge back, it was my wife(now ex-wife, just recent) credit card, but I don't so, I don't remember anything like that, especially since I am a long time Clone user and product lover. I would have noticed something like that at that time.
How can my code key become blacklisted? Did this happen because I use the same key on 2 of my computer's? I rather guessed it would be ok to do or should I have bought a key for each computer?
How about I send the key back to them and let them tell me which one it is, some type of charge back or blacklisted or what the problem could be?