Cannot play Apple TV rented video on my new iMac due to HDCP?

Thanks, I did, and although they could not figure it out, I noticed something else. Apple Support had me check the movie that would not play (Monsterland) on my macbook as well, and on my ipad, and while it did not play on the macbook either, it did play on the ipad. They had me check the macbook by resetting the SMC, as well as NVRAM, and even reboot in safe mode, all on the macbook, since that had the same problem, but nothing helped. But after after that call to the helpdesk, I noticed that I had actually downloaded the movie that would not play, both on my macbook and my iMac. So I thought: what if the downloaded file was seen on the iMac as playing it on a separate device that was not allowed? So I deleted it from the macbook, but then the iMac still would not play it. BUT on the macbook, it suddenly played. Then I deleted the download on the iMac as well, and surprise surprise: now it plays on the iMac as well....

So in short: there is something weird going on when downloading movies from Apple TV that needs looking into. To try and recreate the problem, I rented another video. I then downloaded it on the iMac, and tried to download it on the Macbook. It wouldn't - it gave me the message: 'to download Nomadland (the movie) you first need to remove it from your other device'. Which is annoying, but understandable. However - even though I had just gotten Monsterland to play on the macbook, now that I had tried to download Nomadland, Monster Hunter suddenly doesn't want to play either anymore on the macbook. Weirdly, when I try and start Monster Hunter, it gives me the same error message about Nomadland. It's like some signals are getting crossed...

My guess is that Apple TV wants to prevent showing a rented movie on 2 devices, and therefore blocks downloads. An annoying policy, but more annoying is that there is some kind of bug in the code that does not execute that block properly, it interferes with other rentals as well. And my guess is that because I had somehow managed to download Monster Hunter on 2 devices anyway, that caused a second set op problems.

So the solution to this problem is: remove all downloads in your library, then the movies will play again if you stream them.

Hi, thank you for the fast reply. I know about HDCP, as I have had to deal with it with a previous computer, where I tried playing Netflix-content using an HDMI cable from my laptop.

But with the iMac, none of that applies: no external devices connected, no screen capture software of any kind, I even withdrew screen sharing rights for Zoom (and rebooted) even though Zoom was not running. I even completely shut down my ipad just in case the sidecar-option had something to do with it (also not active). In short, a clean install on a new iMac does not allp[ HDCP-content to be played; clearly an Apple software error. Everythingelse works fine: Amazon Prime, Netflix - no problems anywhere. I have requested a refund for the movie I had rented and will just have to stick to the free content with the subscription. Hopefully, one day it will get fixed.