Hello,
I have one customer where roon plays to device just fine but airplay yields no volume (sound).
What could it be?
I looked at the settings and its all correct.
Volume control in airplay is set to software. This is what it should be. There are not really any other settings.
I figured it out there is a bug in version 2023.5.0, it needed to be updated. Thanks @spockfish.
We’re already at 2023.5.1 - I remember there was an Airplay issue, update to the current version please and test…That would be the most logical to do FIRST IMHO 
I am still having Airplay problems even with the upgrade.
Updating to 2023.5.1 fixed the issue in my case.
Did you reboot after updating? Sometimes needed…
Many times