Could you please provide us with your product’s model number so that we can offer you precise information? 

G34 Surfboard Wi-Fi Cable Modem. I got it set up manually, but there was not a G34 as one of the choices to use the app.

Please make sure that the G34 is providing an internet connection. Then, select the option "ISP cable connected with integrated Wi-Fi."

Please find the link below for the app setup instructions:

http://arris.force.com/consumers/articles/knowledge/SURFboard-Central-Wi-Fi-Cable-Modem-Setup