The only thing I can think are the two well known issues:
1. Firewall stopping traffic to 22.214.171.124 udp port 5353.
2. Multiple mDNS responders… if you are running howl, make sure that howl is running, and that mt-daapd was configured with –enable-howl. Conversely, if it wasn’t configured with –enable-howl, make sure howl isn’t running.
That’s about it.