Kontrol S49 Mk3

I don't know if you need the keyboard registered to use it. Maybe support finds it a bit peculiar that the Kontrol S49 Mk3 should already have been pawned by the original owner , I don't know , but only support can help you with registration questions and no amount of posting here will change that. Get in touch with support here ! Also if you already opened a ticket then do NOT open a new ticket but instead give support time to answer, it may take up to a week during the sale, and if by then still no response then kindly update your ticket with a polite message to let them know that you are still waiting !

And alas I think that the Komplete Kontrol app does not come with Komplete Start anymore. But still , since I am not completely sure of install procedures with respect to the S-Series MK3 then I think that if you have not done so already then add the Komplete Start to your account while logged in at the site and be sure to keep clicking all the way through until Komplete Start has been added to your account . Then that done then turn on keyboard and connect it then install Native Access and log into your account there and then install any hardware service that shows together with any relevant software and see if that helps you get your keyboard recognized.

What you otherwise gets from the keyboard registration is access to the Komplete Select that comes with keyboard per standard and which can be used as base software for upgrades to higher tiers of Komplete software which offers can be seen at the page My Komplete offers when logged in and already having a version of Komplete ! But while there are savings by upgrading then prices still are rather cheap compared to normal prices when there is a sale going on ! Please see the compare page for prices and product content comparison !

Also , you did not state version of Mac OS used so please check the Compatibility of Native Instruments Products on macOS prior to any purchase or install :  https://support.native-instruments.com/hc/en-us/articles/360014900358-Compatibility-of-Native-Instruments-Products-on-macOS

You can find the manual for the S-Sries MK3 keyboard here .

Otherwise , with respect to any registration issues/questions then only support can help you !