How do you have it connected? Have you verified if the MAC filter is on or off? I have an Actiontec MI424WR for Verizon FIOS which utilize a coax. Is your Actiontec router a wireless router too? If so, this could be the problem. You would need to disable or turn off the wireless mode in the Actiontec router. Use one of the LAN ports in the Actiontec and connect it to WAN port in DIR-655. Configure the LAN IP of the DIR-655 if needed. Choose the SSID of your choice, set the wireless security, WEP, WPA, WPA-2, etc.