In this case we need to check the WAN IP since after activation internet is not working, so Please log into the modem admin page and provide us with the WAN IP of the modem. 

If you are already using the Surfboard central App, Please delete the app, Perform a factory reset and connect to the default Wi-Fi network of the modem and login to the admin page 192.168.0.1 and create your login credentials for the modem.

Once you login to it, On the left side of the page you will be having a ‘Connection’ Tab and select ‘WAN’ . On the main screen please check on the WAN IPV4 Address and do let us know about it.

Factory reset steps.

please, disconnect the coaxial cable from the back of the device? At the back of the modem, in the middle section you will see a small hole, inside that hole there is a button, and that is the reset button, please insert a paper clip or a tip of a pen and hold it for 15-30 seconds until all your lights go off, afterwards connect the coax cable back and wait until your device fully boots up.

Wan ip address 8C:76:3F:3A:54:EE

It is the valid IP address; I suggest you to contact internet service provider to reprovisioning the modem by deactivate the MAC address and reactivate the same.