Official comment
@Giorgos > Okay, so you've got the software set to 32bit, and you have ASIO4ALL creating your aggregate, within Traktor's Audio Setup, you should have the ASIO4ALL selected as your Audio Device. On the Output Routing tab, you need to have the Mixing Mode set to External and then configure Deck A for outputs 1 and 2 (or 0 and 1 depending on how it got labeled) and Deck B for outputs 3 and 4 (or 2 and 3, again depending).
If there is a mismatch in the soundcard settings for the samplerate, it won't work. If you don't have an output assigned, the deck won't play.