reason:
pulseaudio is broken and blocks video playback
temporary solution:
restart pulseaudio with pulseaudio -k and retry video playback. it should play.
permanent solution:
1) install pipewire-pulse
2) enable and start pipewire with systemctl --user start pipewire-pulse.service pipewire-pulse.socket and systemctl --user enable pipewire-pulse.service pipewire-pulse.socket
3) check via pactl info if pipewire is active, e.g. “Server Name: PulseAudio (on PipeWire 0.3.48)”
4) retry video playback. now it should start playing without error message.