I am also facing issues with Fedora 34 Workstation edition and my usb headsets. But my headset works for sometime after a reboot. I think it keeps working as long as it is in use by some application but if it is left idle for some time it stops working. Restarting the pipewire service fixes it, as suggested by @ankursinha in reply to my question.
systemctl --user restart pipewire.service