Issues with Apple TV HDCP not playing on iMac Retina 4K, 21.5-inch, 2019 Big Sur 11.2.1

Hello,

I am running a iMac Retina 4K, 21.5-inch, 2019 Big Sur 11.2.1 3.2 GHz 6-Core Intel Core i7, 16 GB 2667 MHz DDR4 Memory with a second Roc 2770Vh1 27-inch 1920 x 1080 display. When trying to play video throught The Apple TV app I get:

The selected movie won’t play on one of your connected displays.

This movie can be played only on displays that support HDCP (High-bandwidth Digital Content Protection).

Try moving the video window to a different display. Make sure the entire window is on the supported display.

This occurs on both monitors after the video plays for around 30 seconds. Screen goes black but you can still hear the sound.

I live in the US (I thought I read that there were problems with Big Sur in non US versions) and the video worked previously in Catalina.

Any suggestions?