You should have received your key now. I have mailed it to both email addresses I have from you. When you registered, a message should have been displayed that it can take a few hours before you receive it (I know, that's bad, but I still haven't found time to automate the process).
Now, the other issue: Audition 1.5. I've just Googled a bit and I see more complaints about many VST's not showing up or being grayed out in Audition 1.5, which was the first Audition version to include VST support, where people get the suggestion to upgrade to a later version (which, as you've seen, helps). Could be because it's from 2004 - Perfect Declipper is a VST 2.4 plugin, and VST 2.4 was released in 2006 (still over 6 years ago)! Most new VST's that come out today are VST 3 plugins, and they will definitely not work in Audition 1.5 - I chose to use 2.4 because I didn't need any 3.0 features so I went for compatibility.
Btw - why would you want to type an email address when registering? You paid using a PayPal account, which means that I get your email address from PayPal. In the very rare cases when that email address doesn't work I try to find a different email address using the info that I have, when that fails people can just mail me and I'll forward the key. Also, what makes you think that you cannot talk to a human being if something doesn't work? I always try to respond as soon as possible to questions, but I cannot be online 24/7! You registered and mailed me just a few hours ago...
If you cannot change to a different Audition version in your studio and hence cannot use the declipper there, just let me know and I will of course refund the money.
Note to anyone else who wants to buy it: Please try it out before you buy! There's a reason that there's a trial version available for download; there are literally thousands of VST host programs out there and there's no way for me to test them all! If you find one where it doesn't work, please let me know!