Do you have access to Cisco.com? I copied below Troubleshooting tips found at
Let me know by repling to your post....
Troubleshooting Tips
If the suggested course of action does not resolve your issue, contact your SP. For detailed information, refer to Chapter 4 of the Cisco 678 ADSL Router Installation and Operation Guide.
If the WAN LNK LED blinks continuously and fails to achieve a solid state within a minute, your Cisco 678 configuration might not be compatible with the SP's server configuration.
Solution: Remove power from the Cisco 678 by removing the power cord from the router's rear panel. Reconnect the power cord and check all cables, especially the WALL cable. If your router still does not connect to the SP, call your SP. Your SP can assist you to correct your configuration.
If the WAN LNK LED turns off after the Cisco 678 has successfully been transferring data between your PC and your SP, the Cisco 678 or the SP's server might have a timeout set.
Solution: Call your SP and provide an estimate of the time (be as accurate as possible) that you remain connected before the Cisco 678 disconnects from the Internet.
If the WAN LNK LED turns on solid for approximately four seconds and then turns off and remains off, this might indicate a user authentication failure. Either your Cisco 678 or your SP's server might contain incorrect user authentication information.
Solution: Call your SP with the amount of time it took before the WAN LNK LED turned off.