I was having the same problem as the original poster and it was driving me mad.
I just fixed it, and for me it was a question of running:
sudo /etc/init.d/mt-daapd restart
I had tried restarting firefly numerous times and I’d rebooted the whole server too, but the crucial difference is that I did it as root
I’m not sure why when my server reboots the script isn’t run as root though, can anyone shed some light?
I’m running ubuntu