No video from Decklink Quad 2 in Cubase 11

I can’t get video playback to work with my Decklink.
The 8 channels are visible in “Video Player” under Studio Setup and I can select the channel I want to use.
The H264 file is playing back on the screen perfectly.
I can play the same mp4 using VLC and Davinci Resolve to the Decklink with no problems.
The latest versions of Cubase and Desktop Video are installed.
I’m running vMix alongside, but VLC and Resolve playback is fine, so don’t think that’s the issue; it’s just Cubase that isn’t working…Any ideas?

Update… Nuendo doesn’t work either…