There is no live session to show it to.
The model takes no (more) video, or the host cannot open this kind of capture.
The user, the operating system or the page's permissions policy refused.
There is no camera, or not the one asked for.
The camera exists, but another application is using it.
The user closed the browser's share picker without choosing.
The call's policy does not allow it: the channel that fronts it is not in the call, or may not show the agent video.
Anything else; see the message.
Why a capture did not start.