Originally Posted by
javabytes
When you are logged in to the router, can you see whether it is getting an IP address and gateway from your ISP? If you are not being assigned an IP address, try a release/renew.
Also, as star_world noted, sometimes cable modems mate with a device that gets plugged into them. If it has bonded to your computer, it may reject your router. You may need to plug your router into your cable modem and then power cycle your cable modem, and then power cycle your router.
to add to this, occasionally, you even need to contact the ISP and have them reset something on their side to allow a new device to obtain an IP address.