Video Share is disabled by the Administrator

Allan thank you Allan for posting this and for doing the legwork to figure out the exact set of circumstances that break video sharing for guests. I used your notes, and reproduced the situation exactly as you wrote it out.  I confirmed that if a Guest uses web client to join meeting, and they connect to the meeting BEFORE the Organizer does, Video Sharing will show as disabled by the Administrator.  If the Guest joins AFTER the Organizer starts the meeting, then Video Sharing works great.  We will advise our users to simply end the meeting and then immediately rejoin (Microsoft gives you a rejoin button after you end the call).

I reported this 'bug' to Microsoft 365 as well.