When clients microphone is not working and you only see the Realtek microphone, means the one for Intel is missing.
A simplified version of the above link from Intel.
- Press Windows + X and select Device Manager
- Expand the Sound, video and game controllers section.
- Right-click Intel® Display Audio or Intel High Definition Audio and select Uninstall Device.
- Click action in menu
- Click Scan for Hardware Changes
Also this link gives you the drivers for this.
