If you’ve experienced one-way audio, it’s likely because of this issue with your FIOS gateway using the factory settings from Verizon:
1) The FIOS gateway comes configured with an incorrect port FORWARDING setting that wipes out most UDP ranges for VOIP audio
2) To fix this, you will need to login to your FIOS gateway
a) Go to FIREWALL, PORT FORWARDING
b) remove the forwarding for UDP TFTP line item (it’s usually a wide-range of UDP ports). If you are uncertain, simply remove ALL of the port forwarding rules – you can re-add the ones you need later
c) after removing the entries, REBOOT the FIOS gateway (if you don’t reboot, your VOIP still may not work)
3) Try the VOIP device again, you should find that the audio now works properly.