@Thor > Please try these steps...
- If you are on a Mac, open the Audio MIDI Settings application, open the MIDI Studio window, then click the drop-down at the top of that window to create a new configuration.
- Check that the firmware is up-to-date (current version 1.01).
- Open rekordbox, click the MIDI panel, then click the DEFAULTS button to reset the controls; you don't need to save the existing settings.