My new Sennheiser G4ME ZERO headset won't send audio to my Mac
If you are using a MacBook with a single 3.5mm jack, you need to make sure you are using the TRRS cable from Sennheiser. That's the one that will have 3 narrow bands on the shaft of the jack (separating the four metallic connections stereo/left, stereo/right, microphone, and ground). Is that how your Siberia works? Single cable?

Also be sure that the "boom arm" is not raised up as that will mute the microphone.