there isn’t a bridge mode as its a modem only device.
the problem you’re having is COX only supplies 1 public ip address. Even though the SB8200 has 2x ethernet ports, cox only allows you to connect 1 device to it (unless you have a business account). So if you’re computer is working, its getting that connection.
So disconnect the pc from the modem, power the modem (and router) off for 10 minutes.
Leave only the router connected.
then power the modem on and give it 2 minutes.
Then power the router on and go through its internet setup (if you need to).
Don’t connect anything else to the modem other than the router.
Hope after following the above-mentioned steps provided (on 12th January) you were able to connect the modem to the router. Able to connect to Wi-Fi Internet.