More importantly connect your phone to the Wi-Fi and check if the internet connection is working.
Note: The Surfboard Central app syncs with the web interface (GUI), so if the app isn’t set up correctly, it can cause the GUI to become misconfigured.
If the GUI page asks for an email address and password for login, it indicates the page is misconfigured. We recommend performing a factory reset. Hold down the Reset button for at least 10 seconds and then release it to reset the gateway. Wait for it to boot up.
After confirming everything is working, start the setup process on the app again. For your reference, please find the link below for the steps to set up the app.
http://arris.force.com/consumers/articles/knowledge/SURFboard-Central-Wi-Fi-Cable-Modem-Setup