First, can you link your repository and/or share your full environment configuration? (e.g. requirements.txt and packages.txt) CV2 requires some binaries be installed which go in packages.txt as they are not python modules.
Second (and more fundamentally), I don’t think cv2.VideoCapture will work with Streamlit Cloud as I think it is using a local camera (as in looking for a camera attached to the Streamlit Community Cloud server containers).