Hi,
First make sure you use a stereo cable
Also ,looking at the specs of the Nitro kit ,it seems only the crash input is compatible with the cymbal . One zone plus choke.
If you want it to act as true dual zone (making another sound when you hit the edge) you have to mod it .
http://www.alesisdrummer.com/index.php?topic=2068.0Beside DIY you will need to loose an input, maybe one tom.
So it may not worth it (also you will have to strike hard the edge to be triggered and don't know if the Nitro kit has crosstalk settings to avoid bow triggering)
Long story short , it's the module not capable of 2 different sounds on the cymbal.
Off-topic:
The DM10 module is also not capable since the edge is also a switch which only fakes an edge sound on fixed velocity (Except on the crash input where you have one sound and choke)
The 2 stereo output cymbals you mention , have an added bell switch and mostly are used on the DM10's ride plus another input , to fake edge/bell fixed velocity sound ,with true bow velocity capable sound , plus choke .
Don't know if the newer Crimson , DM10 MKII , Strike kits offer velocity capable bell/edge zones with choke