And what is your active setting?
Is there an Auto (or similar) setting?
??
To troubleshoot, without HDMI connected, run in a terminal this
journalctl --user -u pipewire --user -u pipewire-media-session --user -u pipewire-pulse -f
and connect HDMI cable (let DP for later).
Try audio settings and watch terminal.
Post terminal output.
Also, you may need to do some juggling like this
https://wiki.archlinux.org/title/NVIDIA/Troubleshooting#No_audio_over_HDMI