Can you confirm that you are enabling USB audio under preferences?
Please note that only UAC audio devices will work with Webcaster X2. As the USB features are beta features we have not tested all USB video and audio sources. It’s possible that some audio devices may not have compatibility. If the microphone is also powered over USB it’s possible the microphone is not receiving enough power and may require an external USB powered hub between the Webcaster X2 and the microphone connected.