Nighthawk RAX40 Internet Connection Issues

Hello all, I'm hoping you can help me. My router is indicating that it should have internet connectivity, and broadcast on 2.4 and 5ghz. All the LEDs are on, yet when I connect any device, either via wifi or ethernet, they are unable to connect to the internet; error usually says "invalid IP" but not always; sometimes it simply says "Connected, No Internet Access". I've tried resetting the router, changing the port that the modem connects to it with, and resetting my network. I don't know why it's not working