When attempting to show your webcam video in a WebEx meeting, issues may arise that prevent that video from being captured by the application. These situations often result in a gray or black screen instead of the expected video of your face.
Troubleshooting a Black or Gray Screen from your Webcam
Check to ensure you’ve selected the correct webcam:
In the Control Panel click on the video icon.
The Video Connectio window will appear. Click on the Camera drop-down menu.
Select the web camera you’d like to use and then click OK.
If this doesn’t solve the issue, verify that no other applications on your computer are also using your webcam; e.g., another webconferencing service such as Google Meet, or a photo capture app like PhotoBooth. Quit any other currently-running applications that may be attempting to use the webcam.