Have you checked the mic is active in your operating system (Windows ?) is selected and the volume is up.
Usually the volume and mixer control is a small loudspeaker icon in the bottom right of your screen in the system tray area where the time is.
right click it and one of the choices is usually "recording devices", left click it and you should see a list of devices one of which should say microphone.
Thats where you can activate it and make sure the volume is up and if theres a mic boost control turn tha up also.
if the icon is not in the system tray you will need to go to your Control Panel then select Sounds and activate it from there



