Set a browser or app baseline
Start with the streaming provider’s supported browser or desktop app. Use a short known-good programme with ordinary stereo audio, and check the Windows output device if the video plays silently. Then reproduce the problem once. If playback fails after you move the window to a different display, record which monitor is active and whether the issue persists after moving it back.
Check the correct screen for HDR
In Windows settings, choose System, Display and the actual monitor or TV. Open HDR for that display and look for the streaming support indicator. Microsoft notes that an external display can behave differently in duplicate and extended desktop modes, and battery settings may affect streaming HDR on laptops. Compare the same title in SDR if the colours suddenly look wrong. Do not assume an HDR change improves a stream whose actual source is SDR.
Collect a useful support description
Write down the Windows version, graphics driver date, browser or player build, display model and connection type. Test without browser extensions only in a temporary profile if you need to isolate one. Leave your account and normal profile intact. Capture the error text and the exact programme and time without showing private playlist URLs or saved login details.