S4 does not work with Traktor DJ 2.
Traktor DJ 2 is very limited when it comes to controllers. It only supports a handful. It also got abandoned ~4 years ago. And even if it would work, Traktor DJ 2 only has 2 decks.
The s4 is designed for Traktor Pro (2, or 3 if you use the mk3 model)
It should come with a key for that, if the seller gave you a transfer key. You should ask him for it. If the seller said he sell it without software .. you kinda screwed yourself.
