Are you represented as a blank (gray) window in JackTrip, instead of it showing a video feed from your camera?
Problems with video are most often caused by camera permissions settings in your computer's operating system. Please review one of these guides to ensure that JackTrip is granted access to your camera:
If you are using the Desktop App, please make sure that "JackTrip" has access to your camera.
If you are using a web browser, please make sure that your browser has access to your camera. In addition, you may need to review your browser settings to allow JackTrip's web application to access your camera.