Have you seen this error?

Access Denied

You don't have permission to access "http://payments.xfinity.com/new" on this server.

Reference #18.627b3217.1706824021.90af64b

If so what I did to solve it was install firefox and went straight to xfinity.com billing and it worked fine. It seems that if a browser has any extensions etc the site refuses to load. So here are the steps

1. Got to https://www.mozilla.org and download ``Firefox`` 
2. Install on your machine and skip any [Edited: "Language"] it asks you.
3. Go to xfinity.com sign in
4. Go to billing
5. Pay bill

[Image Removed: "Personal Information"]

Best of luck ; also though I didn't test it you might be able use edge or chrome as well.