With Windows 10 version 1803 (April 2018 update), 1809 (October 2018 update), 1903 (April 2019 update) and later, Microsoft changed the behavior of microphone app access setting so that it affects desktop applications as well.
- 9 Feb 2019: Updated the guide to include suggestion about turning on the microphone for Win32WebViewHost app
- 3 May 2018: Article published
To fix this do the following:
1. Go to Windows settings and select Privacy
2. Select Microphone and switch on the "Allow apps to access your microphone" toggle.
3. Under "Choose which apps can access your microphone" check that Win32WebViewHost (later renamed as Desktop App Web Viewer) is turned on as some desktop applications will need it.
4. Restart those applications where you've wanted to use the microphone.
5. (Optional) To block apps access to microphone you will have to toggle microphone off for each app. You will have to do this after each new app you install. It's recommended that you do not turn off microphone access for Win32WebViewHost (later renamed as Desktop App Web Viewer) as some desktop applications will need it.
Thanks to Shane and RatusNatus for the tips.