Could be related to recent change in how audio work. Need to update the guide it you confirm the following things solve your issue.
In your sys-audio vm:
qubesdb-write '/qubes-audio-domain-xid' 1
systemctl --user restart pipewire
Does it work now ?
If it work, try to set the audiovm of sys-audio as itself.
In dom0
qvm-prefs sys-audio audiovm sys-audio