21" iMac TV+ app or streaming TV+ via Safari results in black screen after approx 35 seconds of viewing

Updating to macOS Big Sur 11.2.3 did not remedy the problem. Also, I tried downloading the video (for offline use) as per a suggestion. Playback of that immediately results in the error message: "This movie can be played only on displays that support HDCP (High-bandwidth Digital Content Protection)." For clarification, I'm just trying to view it on the 4K 21" iMac's screen. I can't think of any reason why an Apple iMac Computer that was purchased last summer wouldn't support HDCP.

FYI: Screen sharing is off.

Suggestions?

Thanks, I referred to the help document. Alas, its suggestions didn't remedy the problem. I think it may be an issue specific to this BTO configuration, as others with the same BTO configuration, indicated in subsequent replies that they too are also encountering the same problem.

I spoke with Apple Support on twitter, and they escalated the issue to one of their senior advisors. We tested the issue creating a new test user account and were able to repeat the problem. Diagnostic information was recorded and submitted for further diagnosis. I have a follow-up troubleshooting appointment scheduled for Monday.

I spoke with my Apple advisor again today.

Today's troubleshooting steps included creating a partition and performing a clean install of Mac OS Big Sur on it, and then booting up from that newly created partion. This differed from the previous test account we had created, for this time a full clean install of OS Big Sur was done. Alas, the issue of playback going black after approximately 30 seconds when streaming content via AppleTV+ as well as immediately resulting in a black screen with a HDCP error message when attempting to playback a video that been downloaded via AppleTV+ still occurred in the newly created environment.

Update: I spoke with my Apple senior advisor late this evening. I was informed that the issue has been escalated in engineering and is now being treated as a "bug", and at this juncture there is nothing they can do other than wait for the playback issue to be addressed in an upcoming software update. In the interim, I suggest using an alternative browser, such as Firefox, as the playback issue on this BTO iMac configuration only seems to impact Safari and the AppleTV+ app. and, as previously mentioned in this discussion thread, AppleTV+ content when viewed in Firefox doesn't result in the blacked-out screen & error message.

Thanks for the Firefox tip. I mentioned it to my Apple advisor.

Note: it's been over a month and the folks at Apple still haven't been able to resolve the issue.