An interesting one I've run into a few times recently, after a major build update on Windows 10 all microphones stopped working. The microphones themselves were fine, and worked as normal on any other device. However on this one machine, they would no longer function.
- Drivers were updated, this wasn't the issue.
- Bios was updated, also not the issue.
- Sound drivers were purged from the system and reinstalled. Nope.
- Removed the upper and lower filters from registry entry, still nothing.
Then while clicking around the Windows 10 settings menus, and stumbled upon the privacy section. There was a setting "Allow apps to access your microphone" that was disabled. Enabling this resolved the issue.
This setting can be found by clicking Start > then click Settings (the cog) > then click Privacy > then click Microphone. Look for the "Allow apps to access your microphone" slider and make sure it's set to ON.
I hope this helps someone! :)