For some time, our Sonos sound bar went off when we used our XR11 remote to turn off our TV.  Then it stopped.  The XR11 always worked to control the Sonos Sound Bar volume but at some point, the sound di not turn off when we turned off the TV, which was annoying -- we would have to turn the volume all the way down.  I posted about it here: 

Mystery solved!  At some point, I must have changes the topical fiver connections from the TV to the cable box.  Turning off the TV does noting for our cable box, so the sound signal still came to the Sons.  I moved the optical fiber back tot he TV and, when the TV goes off, the Sonos goes off.  Mystery solved.