It is required to set extra permissions for web-cam and microphone usage by apps in Windows 8\8.1 System settings.
Windows 8
1. Move your mouse cursor to the upper-right corner of your screen to reveal the Charms bar. There click on Settings:
2. Next, click on Change PC settings at the bottom-right corner.
3. Navigate to Privacy.
4. Click on the Webcam option and make sure that the "Let apps use my webcam" flag is set as in the picture below.
5. Navigate to Microphone and make sure that the "Let apps use my microphone" flag is set as in the picture below.
Windows 10
1. Go to Start and click on Settings:
2. Navigate to Safety:
3. Choose Webcam on the left-side panel and make sure that the "Allow apps to access your camera" flag is set as in the picture below:
4. Scroll down and make sure that the "Desktop App Web Viewer" and "Allow desktop apps to access your camera" flags are set as in the picture below.
5. Choose Microphone on the left-side panel and make sure that the "Allow apps to access your microphone" flag is set as in the picture below:
6. Scroll down and make sure that the "Desktop App Web Viewer" and "Allow desktop apps to access your microphone" flags are set as in the picture below.
Windows 11
1. Right-click on the Start option and select Settings:
2. On the left-side panel, navigate to Privacy &security and click on the Camera option as in the picture below:
3. There, make sure that the "Camera access" and "Let apps access your camera" flags are set as in the picture below:
4. If necessary, scroll down in the same menu and make sure that the "Desktop App Web Viewer" flag is set as in the picture below:
5. Next, in Privacy & security select Mircophone:
6. Make sure that the "Microphone access", "Let apps access your microphone" and "Desktop App Web Viewer" flags are set as in the picture below: