Airplay on apple TV4K works with YouTube but not other videos
I saw this questions in the community but no answer. We use apple TV4K to mirror shows from our iMAC to TV screen via TV4K. Recently it stopped allowing all videos to mirror. The sound comes through but not the video. The video aspect DOES work for YouTube videos (suggesting the setup is fine) but not other videos shown on the web via streaming (various providers - pbs, Roku web etc). I've tried restarting everything and updating but no help. Is this a known problem that has no fix? Why it is selective for certain videos?
Apple TV 4K, tvOS 15