With the SDI G2 model camera, the audio will embed over the HDMI and network only, but not over the HD-SDI. 

With the USB G2 model the audio will embed over the USB and the network, but not over the HDMI. A microphone directly into the audio line on the back on the camera will not work.

A microphone needs an amp to function and control it's level, the camera does not have any kind of amp or preamp to handle a mic level signal.

If you delete a mic in Device Manager, when you connect the camera to the PC again, it should automatically load the correct drivers for the camera.

If you disabled the mic in sound settings or deleted it from whatever software you were using, you may just need to re-enable/re-add the camera as a mic source.