Some serial numbers have limited activations, which means you will have the possibility to activate the product for a limited number of times, after which it's rendered useless.
Secondly, I don't think the email you used should be addressed for this issue. Use the following page and click on Contact Support, then enter your inquiry, and someone will assist you: https://soundsoap.uservoice.com/
I recommend this way because the developers are the only ones who have access to the serials.