Go to your router (the thing with 2 or more antennas sticking out of it, usually sitting right next to your Modem), and unplug the power and the Ethernet cable that is going into it. Wait 5-10 mins, and plug the power back in, and wait for the Power light to come fully on. Then, connect the Ethernet cable to it, and wait for the rest of the lights to come on (not all of them will). Then, look at your Modem. if there is a light constantly flashing that says PC Activity, your WiFi should be back up and running.