I'm going to assume you are on cable internet. I found the following to work.
Put the router switch to on.
When you open the browser the wizard starts and tries to acquire an IP. IMO the wizard blows. Open a second tab and navigate to the router's gui.
Click on the internet /LAN tab. " Under Method of acuiring IP address" choose "Acquire an IP address automatically from DHCP server"
Click apply
If that doesn't fix your issue add on the following.
Connect your computer to the modem. Acquire an IP and verify that you have internet.
Now connect your router back to your modem. Connect the computer to the router. Navigate to the routers gui.
Open a command prompt. and type "ipconfig /all" Now press enter.
FInd "Ethernet adaptor local area connection" Write down the physical address
Go back to the internet /LAN tab. Scroll down to advanced settings.
Under "Internet MAC address" click "use this address" and enter your physical address.
Click apply
Hope this helps
Nick