said by sturmvogel6:You may want to:
1. Assign the VoIP device a fixed IP, e.g. 192.168.1.30 or at least note from the DHCP logs what IP it has.
2. Put this IP in the DMZ of the router
3. Reboot the VoIP device
4. Check that the IP is still the same for the VoIP device
I am not sure why this would be necessary because it has been communicating through the router for over a year without any problems, the only change is the ISP.
I believe it must be a contraint in the modem that prevents it from functioning. But I dont know what it is or how to fix it.