I created a camera tracking animation: a dinosaur walking in my street. Everything worked fine until I deleted the video background and added a new one. In render view I can see the result I want: my 3d dinosaur, the shadow catcher and the video at the background. When I render it, the video does not show. The background is a gray color. I don't understand why it doesn't works, because the first video background did render in the final result.