When connected to an external monitor, videos are black and the audio won't play

A_Shah89 wrote:

https://www.redditstatic.com/desktop2x/img/renderTimingPixel.png

When my 2018 MacBook Pro is connected to an external monitor (Dell, using HDMI cable and dongle) while I play videos, they do not load. Instead, the progress bar on the video continues, but the screen stays black with no audio. If I switch to another browser, like Chrome, this issue disappears, and the videos work perfectly fine. Some websites this has been occurring on for me are Netflix and Udemy. What can I do to fix this? The settings on the website allow for it to auto-play media, pop-ups aren't blocked, and content blockers are not enabled.

If Chrome works I would use it...(?)

Get help with video issues on external displays connected to your Mac - Apple Support


If your external display isn't detected or appears blurry when connected to your Mac - Apple Support

Using 4K displays, 5K displays, and Ultra HD TVs with your Mac - Apple Support


 Connect a display to your Mac - Apple Support

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if in doubt search the developers website or contact their: Support/Help/FAQ/Known issues/compatibility/Updates

Contact a third-party vendor - Apple Support

Contact a third-party vendor - Apple Support

see if there is anything here:

One possible solution for those having issues around (Dell) USB-C monitors not detecting MBP M1 or Mac detecting monitor