Tried with Apple TV+ with 3 atmos listed titles, also Netflix with a couple of titles and finally my movies with the same results no atmos, tried a full reset with nothing set up and it shows atmos if available in the audio settings, also tried a reset then setting everything back up the way I had it still no atmos and then tried just switching atmos off and rebooting but still nothing. That’s when I tried a couple of discs and they played in atmos verified by the front display on the avr and also via the info button. So that led me to accept it was the Apple TV and just wait for the next update. Sorry should have said I did check that Dolby was set up and it isWhat app or streaming service were you actually attempting to get Atmos in association with?
There's nothing unusual about Atmos being conveyed to an AV receiver in conjuction with myltichannel PCM if using an Apple TV. The Apple TV uses Dolby MAT to fascilitate Atmos so will convey the Atmos metadata with multichannel PCM as opposed to bitstreaming the DD+ encoded audio package associated with streaming serrvices inclusive of the Atmos metadata. The AV receiver should however indocate Atmos on its front panel display if and when such Atmos metadata is present though.
Have you correctly configured the ATV's audio output as instructed here:
Apple TV is designed to deliver the best sound experience that your home entertainment system supports. Learn which audio formats are supported on Apple TV and the setup you need in order to play sound in the highest quality.support.apple.com