i have no contact with the previous owner i have the receipts can anyone help me
There's a link at the bottom of this page that will get you to support - https://support.native-instruments.com/hc/en-us/articles/360001301669-My-Serial-Is-Already-Registered-to-Another-User-Account.
They're the only people who can help with this. Be aware that you'll need the older version of Komplete Kontrol for an S25 as it's a MK1 keyboard. You can download it from here once you get the registration sorted out - https://support.native-instruments.com/hc/en-us/articles/360000313457-Komplete-Kontrol-Legacy-Installers-for-Older-Operating-Systems.
