Xfinity customers and perhaps other ISP's as well are having issues connecting to specific websites all over the east coast.

Connections to some websites cannot be established: twitter, github, stripe, battle.net, xfinity.com

https://downdetector.com show how wide spread the problem is.

Edit:

Some reports from xfinity customers in the bay area as well experiencing issues. Connection to AWS for some affected as well

Edit 2:

As of 9:15AM Est, services are back to normal for me. It appears Xfinity is resolving their issues