Check Privacy Settings for microphone
Click the Windows button, the type 'Privacy'
A few options should appear. The quickest way to get to it is by clicking on the Microphone settings icon as highlighted below, but you can click on Privacy Settings at the top and navigate to the microphone settings from there.
Make sure that the toggle for 'Allow Apps to access your microphone' is on, then scroll down for more options.
Make sure that the app you want to use is listed in the 'Allow desktop apps to access your microphone' setting.