Is it no audio or 1 way audio? The ports look good. All should be UDP except 5566 which is TCP.

Go to one of the phones in DB Programming and then go to IP Settings\Network Configuration. Verify that the Audio Stream Receive Port has not been changed. Should be 5004 by default.

Other than that, I would test the connection with the firewall wide open (no ports blocked) and see if you have audio. Also, if possible I would bring the phones right next to the HX 5000 and see if the audio is there at that point. Maybe the ports are being blocked on the far end as well?

Also, try changing the NAT address type to Auto instead of NAT and see what you get.

Good luck and let us know what you find.