When I push the power button on it lights up then turns off but the master stay on. I have a traktor kontrol s4 mk2.
Maybe check the manual including the section 10 about setup ?
Have you opened Traktor?
No i bought it used
Controller Editor should also detect the unit - it is a good troubleshooting step to figure out if the unit is functional. If so then your unit will switch into it's MIDI Mode.