Hi,
Start by checking the microphone settings if it's not mute or need adjustments.
- Right click on speaker icon on the bottom right hand corner and select Recording Devices.
- Once open right click on Microphone and select Properties.
- Click on Levels tab and make sure it's all the way up to 100%.
- Do also check if it's not muted.
- Click Apply and OK then try using the Microphone again.
Here are more troubleshooting steps you can try if these first tips don't work.
https/support.microsoft.com/en-us/kb/266677