How to Activate New Modem

See the instructions at https://www.xfinity.com/support/articles/xfinity-app-activation .

Adding some other options;

Connect it to the coax line and power it up. Let it fully sync up with the system, and check that the front / top panel indicator light(s) are steadily lit. 

Then 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.

Hello There @Slagdor ! Activating your new modem is simple and easy via the Xfinity My Account App! 

1. Download the Xfinity app for free from Google Play or the App Store.
2. Sign in using your Xfinity ID and password. If you don’t have one, you can create one from the sign-in page.
   • Note: If you’re activating a Gateway, you might be prompted to start the activation as soon as you sign-in. If you aren’t prompted, proceed to step 3.
3. Once you're signed in, select the Account icon from the top-left corner of the Overview tab on the Xfinity app.
4. Select Activate xFi Gateway or Modem under the Devices section.

You'll be prompted to scan the modem sticker from the box or the modem itself. 

And you're all done! 

Once you've got that new modem activated, you can use our Xfinity Return 

Center to find the nearest drop-off location for the old equipment!  Hope this all helps!  

You can also find a ton of great tips/tricks on how to use your Xfinity Servies via our YouTube Page

@Slagdor 

Did any of the suggestions that you were given work out ?