Note: The following assumes you are using a Playbar, Playbase, Beam, or Amp connected to your TV.

You need to train the Sonos device to read the output of the Xfinity remote.  First, make sure your TV audio is set to “Fixed” output, no variable.  Then do the steps in the following link:

Set up a new TV remote with Sonos home theater speakers

1. I don't know how to check for "fixed output"

2.  We have gone through the steps 4 times. Even changed the batteries in the remote. Sonos can not find the remote for some reason.

3. Yes...we are using the Beam.