Like Scottray said, test the cables. It's the single easiest thing to test and confirm if it's working or not. Cat6 is more of a hassle to cable than Cat5(e) despite using the same wiring setup. It's very easy to not push a wire far enough in to the cable end. I've been wiring this stuff for 20 years and Cat6 took a more concentrated effort to ensure proper wiring.
Once you know your wires are sound, you can start diagnosing the rest of your network, which typically is more time consuming than a wire test.
After you confirm if the wires are good, then look at your router/switch setup. Isolate it off your Internets Modem (assuming it's not an all in one unit). Ensure the problem is local to it and not an internet. If that's working...