blue flashing light

First. Check here for info on any possible local outages;

https://www.xfinity.com/support/status 

Use a cell phone internet service, a public WiFi hotspot, or a neighbor's internet if you need to, to check it.

Why is my Xfinity router flashing blue?

It is trying to update, but the signal is too weak, or you are not connected to the Internet.

https://www.google.com/search?q=Why+is+my+Xfinity+router+flashing+blue%3F