I assume you have Cable broadband and it's a Cable Modem that you're connecting the router to?
That being the case, switch everything off and leave without power for about 5 minutes. You can leave the connections in place. Power on the Cable Modem and once it has booted up fully with all lights displaying correctly, power on the router. Let it also boot fully and then boot the PC.
If that still doesn't work, and a direct connection from PC to Cable Modem does work, there should be an option in the router's settings to clone the MAC address of the PC's network adapter. Try doing that so that the Cable Modem detects the same MAC address when the router is connected instead of the PC.