Purchased movie is not the correct format to play

I just purchased The Lego Batman Movie on Apple TV for my kid. When I try to play the movie, I get:

Content Not Available - This type of content is not currently compatible on your device. To play, try again using an Apple device.'

The device I am using is a Roku Streaming Stick+, but which we just finished watching another Apple movie on. Additionally, we were having trouble purchasing the movie through the app, so I went on my laptop and bought it through Apple TV there.

If we try to screen cast from the laptop, we get 'This video is in a format that can't be streamed to this TV'.

I struggle to understand this difficulty, especially seeing as how all our other purchases work just fine.

Yes, we have updated Roku to latest version. Same with Apple TV. Yes, we have gone to the (unhelpful) article ostensibly governing this issue (here: https://support.apple.com/en-gb/HT207060)

Any help would be appreciated.