Have you ensured that the FFmpeg hub component is installed?
ffmpeg hub
I’ve also written a fixed component for non-virtual env installs
Heres how to use the custom_component
Please create a custom_components folder in the home-assistant config folder (The folder were configuration.yaml is) and then a camera folder under the custom_components folder.
Then add the following file in to the camera folder as onvif.py
github gist onvif.py
Then restart Home-assistant