Sound volume icon on TV is crossed out but sound works.

In most cases, you can’t. Sonos is at the end of the chain, not in the middle, so getting a display on top of the data coming in isn’t something that can be done. 

I'm not a techie but I somewhat understand what you said.  Thank you for replying.  What I fail to understand is how the most highly rated TV by Consumer Reports and a highly rated soundbar like Sonos, both state-of-the art and very expensive, don't work together on the simplest element, the volume icon.  It doesn't make sense.

The Sonos isn’t part of the video stream. Nor is it a part of the TV’s electronics. It’s external to that. The TV manufacturer declined to make any standard feedback loop for external devices to feed back volume information to the TV, and to allow the TV to show that information on the screen. 

That might be a function of HDMI CEC, I’m not sure, but I’ve not seen anyone implement that feature, if it is. It’s entirely possible that some have, and I’m just not familiar with their TV sets. For Sonos, the only two devices that use HDMI CEC are the Sonos Amp and the Sonos Beam, and the soon to be released Sonos Arc. 

While I recognize that you want what you’ve always had, why is it so hard for your ears to tell if something is too loud or too soft? What benefit does the on screen display offer to you? I get that it’s some sort of UI affirmation, I’m not sold on the need for it, which could be just me. 

Thank you.  I understand your explanation and appreciate your time.  I won’t bother you with all the reasons my wife and I feel the volume display is important.  Life experiences vary from person to person.  Our situation makes the absence of a visual volume display very frustrating and unnecessarily time consuming and inconvenient.  Moreover we paid for an important TV feature, which Sonos prevents us from using.

Sonos prevents you from using? I thought you said you understood the explanation?

Choosing to use an external speaker (ANY external speaker) made this inevitable.

Not inevitable, more completely random. I have three Samsung televisions attached to either Beam or Amp. Two indeed show no volume numbers, but the third one does (even though in steps increasing with 2, i.e. only showing even numbers)

I’ve found the implementation of CEC standards on TV’s to be incomplete at best, and utterly scattershot at the worst. Changing the input from cable to streamer used to start up my old Blue-Ray player (since gotten rid of).  It kept happening until I turned off CEC.   

Since it works on some TVs and not on others, it doesn’t seem like Sonos is preventing anything. 

I confess that with different broadcasters transmitting programs at different audio levels, I tend to let my ears tell me if the system is loud enough rather than a number on the screen. 

I wonder (just wonder, I don’t know) if what is being shown is the volume that the internal speakers would be at if they weren’t muted, or bypassed.  And not the volume actually playing through the external speaker.  I have certainly seen that, although that may or may not be the case in your example.