As Traktor is not supported by Automap, the 'learn' button on the Nocturn will not learn parameters in Traktor. You'll need to create a Midi Client and use Traktor's own learn system to assign parameters to control.
Make sure you are using the latest version of Automap and Traktor Scratch Pro.
First open Automap and go to the Software Setup Tab. Click Advanced in the list of DAWs. In Advanced make sure the MIDI Ports say "Automap MIDI" for Out and In.
Click on a MIDI Channel check box to check, or turn on, a channel.
Next click on the Automap > Mixer/Plugin Mappings Tab. Select the Channel you just turned on, Channel 1. Click Edit Mapping. This will open the Control Map for your Nocturn. Assign each parameter a CC Note. Once each parameter has a CC Note you can use Traktor to Learn these CC Notes.
In Traktor > Preferences > Controller Manager > Select the Device Generic MIDI and set the In-Port and Out-Port to Automap MIDI.
In the Assignment Table click Add In... and choose the Parameter you wish to assign. For example to map the Cross Fader choose Mixer > X-Fader > Position.
With the Assignment you just made highlighted click the Learn Button under Device Mapping. Now move the control you wish to assign, in this case the Cross Fader.
The CC Note will be read by Traktor. The Cross Fader, or other Parameter, is now mapped.
Use the Assignment Table to create any other Mappings you wish.
You can also search online for TSI files (Traktor Mapping Files) created by other users. Note however those TSI files may correspond to different MIDI Notes in the Automap Channel 1 > Control Map you have made for your Nocturn so it may be easier to create your own.