HikinenM: I have the same issue. Atmos works in certain scenarios like Atmos access app and Netflix but no sound when playing Cyberpunk 2077. AVR sees that Atmos is in use but no sound can be heard.
Tingerlinguss: I have the exact same problem It does not look like a hdmi handshake issue.
I finally found a fix - apparently the latest Dolby Access app on Windows is trash. Go here:
https://www.filehorse.com/download-dolby-access/old-versions/ -- and download 3.2.169, and install it. It was say a newer version is installed, but install this over it anyway. Select Atmos in windows sound settings and good as gold, work immediately, didn't even have to restart. -- I hope that works for you too.