Just purchased this modem and tried to activate on Xfinity and the tech I was working with was unable to see it.  The top LED on the front was a solid green, and the bottom one was blinking green.  After providing the MAC address to the tech and waiting, I was never able to get a proper internet connection.  I WAS able to get their ‘activation’ screen up, but when following all the steps I would end up back at the initial activation screen.

To me this sounds like an Xfinity problem, but the fact that the tech was unable to ‘see’ my modem makes me unsure.  When we were done I just plugged my old modem back in and all worked fine.  So now my new modem is waiting for me to make another run at this whole installation.  He seemed to think that there may be a problem with the new modem, which is why I am here to see if anyone has any ideas.   I really don’t think I should need a tech to come install this.