So, from the way the Qunexus outputs CV, this is exactly what I would expect to happen. The Qunexus multiplexes the gate and pitch CV signals onto a TRS connector, with the pitch on the tip. The CV module only cares about the signal on the tip of the TRS (see for yourself).
Right now there is no official (read: dedicated bit) way to connect an external gating signal into the littleBits system. The control voltages that the Keyboard module produces are actually kind of a hybrid pitch-gate combination; they turn on to the correct pitch when you press a key, and drop to zero when you release it. Unfortunately your Qunexus doesn't output CV the same way.
If you're up for a little hacking, there's a way you can get around this. You'll need a Y cable plus two regular 3.5mm cables, stereo or mono. Cannibalize one end of one of the cables so you have two exposed wires, one from the tip and one from the sleeve.
Build this circuit:
power > CV > oscillator > envelope > [whatever else you want] > speaker
Connect your non-cannibalized cable from the Left output of the Y cable to the input of the CV module. Plug the cannibalized cable into the Right output of the Y cable. Connect the exposed wires to a proto bit (either of the two screw connectors, make sure the 3 jumpers are all in place). Connect the tip wire to the middle screw terminal, and the sleeve wire to the screw terminal on the side that says GND. Snap the output of the proto to the "trigger in" bitsnap on the envelope. Voila, you should have a gated CV signal.
This is the best method I can think of until we get a gate bit (hopefully soon!)