You will need to reset your cable modem for it to recognize your router. Most ISPs and/or cable modems remember the MAC address of the device that you registered when you start using the service. In most cases, power cycling the modem (disconnect the power, leave it off for 2-3 minutes, and then turn it back on) should resolve the problem. Of course, this will only work if your cable modem is not powered by a backup battery, in which case you might need to disconnect the battery too. In rare situation, you may need to call your ISP to register the right MAC address. Hope this helps.