Loss of voice audio on center channel speaker

I have a Dolby Atmos Home Theater system with a 4k Xfinity cable box.  During the NFL season I could not hear the referee announce the calls.  Found that the ref was not being broadcasted over the center channel speaker even though the announcers were.  Went to my nephews house who has a 5.1 system with a 4k cable box and he did not have this issue.  In Jan I returned my 4k box for another one.  Problem did not go away.  I have also discovered that on the TV show The Voice the announcer, judges and contestants come over the center channel fine.  But when the contestants sing their voices disappeared on the center channel.  When I play the You Tube app via the 4k box I do not get voice audio on the center channel but when I play the same You Tube content via my Apple TV everything is fine.  

I have spoken to Xfinity CS and they sent out the technician who I demonstrated my issue to and he was completely befuddled. His suggestion was to replace my 4k box with an HD box which I do not want to do.  I would like to know if anyone else is having this issue.  Thanks.