SB8200 is just a cable modem so we can only check the modem whether it is providing internet on direct connection without router. So disconnect the router and power cycle modem for a minute then connect any device like laptop or computer to the modem ethernet port and check for the internet if that works fine then again restart/power cycle modem for a minute then connect router to the modem ethernet port to setup Wi-Fi if you can able to access internet from the modem and with the router internet does not working then you have to check with your router manufacturer only.