I have to ask the obvious question: is there any chance you entered the code for SoundForge to register ACID Pro and vice versa?
If that is not the case then you should be able to contact Magix Sales without having to buy a support ticket. Use the Contact button in the footer of every forum page and once on the page, use the option to contact the Sales Team.
As both registering the product in activation procedure and registering the product on the Magix customer site does not succeed I would check the numbers entered again. Often letter O is mistaken with digit 0 (or vice versa) and capital I (i) with lowercase l (L) - although serial numbers usually are all CAPS. Sometimes even a V can be misread as W or the other way around.
That as an addition to the piece of advice given by @emmrecs.
Aside from that, ensure you do not mix the Serial number with the order number or product/item number also listed in the confirmation email.