Just installed Volumio today and had this issue with my HIfimediy DAC
It wasn’t easy to find an answer so I hope this could help anyone has this issue.
the DAC was connected to usb but no sound from pi.
I had to do this to make it work:
sudo apt-get update sudo apt-get install git-core sudo apt-get install binutils sudo rpi-update sudo reboot
now it works like a charm.