This isn’t specifically a problem with Audacity, but I’m trying to get help anywhere I can.
I think this started after the Win 10 Anniversary Update.
After a system boot, my webcam mic shows up as the default mic, and enabled, but it doesn’t pic up any sound. If I try to record with Audacity, it doesn’t even start recording.
I can get it working by disabling, then re-enabling the mic. Then it works until the next reboot, but sometimes it will work. I’ve tried switching between the Microsoft drivers, and the Logitech drivers. Both work and fail intermittently at boot.
As I said, this isn’t limited to Audacity (where I wouldn’t be using the webcam mic anyway). It’s a problem before the audio goes to any app.
After a system boot
We can sometimes get people out of trouble by telling them to clean boot their machines. Many of them haven’t been restarted since Eisenhower was president and they collect bad settings, contradictory environments and preferences. You strike a different bell. How often do you restart? Once a week or sooner isn’t normal. If you are required to do that to keep it running, then you may have far larger problems than just the microphone.
Koz’s clean boot is Windows Start button, then hold SHIFT and click on “Shut down”.
If it’s less than ten days since you obtained the Anniversary Update, then you can open the Settings app, Update & Security > Recovery > Go back to an earlier build.
Or you can do “Reset this PC” from the same Settings pane, which will reset your machine to how it was when you bought it (so before the Anniversary Update).
You can get more help here: http://www.tenforums.com/ or of course the Microsoft forums though I would try tenforums first.