Go to the MAGIX website and log in to the "My Products" section. All registered serial numbers associated with your email will be listed there.
ACID Music Studio 10 serial numbers to work can be tricky because ownership of the software transferred from Sony to Magix, and older activation servers have largely been shut down. If you have a legitimate license but the key isn't sticking, you are likely hitting a server handshake issue or a registry conflict. magix.info Troubleshooting Activation Issues acid music studio 10 serial number work
If previously registered, it should be under "My Products" at Physical Box: Go to the MAGIX website and log in