What is the easiest way to register my new third party modem? I have already confirmed it is compatible, powered, and hooked up correctly. I have already wasted a day attempting to "discover" the new modem and activate it via app/online to no success. I do not have the patience to spend the day with Comcast customer service trying to speak to an actual human.
Connect it to the coax line and power it up. Let it fully sync up with the system ("DS, "US", and the "Online" lights are steadily lit). Connect a computer to it and open up a browser. You *may* see their "Walled Garden" modem self registration page. If so, follow the screen prompts. Have your mobile telephone number, your Xfinity username and password or the account number and telephone number associated with your Comcast account handy.
If not, try calling 1-855-652-3446. That is their device activation line.
If that doesn't work for you, you can call 1-800-comcast and tell a rep that you would like to have a new modem provisioned for service. Have the RF / CM / HFC MAC address and the serial number of it handy when you call.
Customer service was able to register and activate my modem. It took multiple calls and many "agent" prompts to eventually get connected to someone. The whole process was approximately 40 minutes.
Glad it got sorted out !