Rekordbox Licence wrong Mail

Hi, on 1.10. In 2015 I bought Rekordbox. At that time, I still registered with a mail address at Pioneer, which I no longer use. Now I have a new Mac and wanted to activate the current version - with my current Pioneer account and access. Then unfortunately comes a note that the mail address is wrong. Unfortunately the serial number is linked to a wrong account. What can I do? On the laptop, the version runs perfectly. I have always updated. From Rekordbox 3 to 4 and to 5. :( Thanks for any help. Toby