What other devices are connected to your TV? Do you have Anynet+ enabled? Have you tried disabling eARC on the TV? Are you using the HDMI cable that came with the Arc?

I have verizon set top box and chromcast. I disconnect chromcast from TV. I used HDMI cable with the ARC. Nothing has worked so far.

I called Sonos tech support. She run diagnosis. I was told that the signal not coming from TV. She said that Sonos ARC needs eARC to work and the TV does not have eARC. She asks me to contact Sumsung for help.  This does not make sense to me. eARC is backward compatible, Without eARC, you should get little degraded sound from the soundbar, but it should be working. I have done extensive search on the internet. People using TVs of different models have reported same connecting issue. Sonos blame the problem to TV manufactures instead of trying to solve the problem that many users are having.

I will return the soundbar to Sonos if this problem can not be solved. 

The support person is incorrect, you need an ARC connection, but eARC is only necessary for non-streaming HD formats.  

Try this:

Disconnect everything from your TV including the Arc and unplug the TV and Arc from power for a couple of minutes. Plug them both back in but keep everything disconnected. Make sure Anynet+ is enabled in the TV settings. Run TV Setup under the Arc’s settings in the Sonos app and follow the app instructions. When the app instructs you to, connect the Arc to the TV’s HDMI ARC port using the Sonos-supplied HDMI cable. After the Arc has been successfully connected to the TV, power off the TV and turn it back on to see if the Arc stays connected. If so, connect the Chromecast and test again. Then connect the Verizon box and test again.

Thank you very much GuitarSuperstar for the comment.

I followed your recommendation to test the speaker connection. I was able to reproduce the specific issue for the loss of speaker connection. 

If I turn of TV (power off TV ) and the  Sonos ARC soundbar is disconnected when next time the TV is turned on. ( 

If the power cord is unplugged from outlet, Sonos ARC soundbar stays connected when next time power cord is plugged back and TV is turned on.

It is clear that the TV does something to prevent the Audio signal transmitted to Sonos ARC through the HDMI connection if the power connected to TV even if TV is powered off.

The TV is Samsung UN85JU7100. 

I am thinking to add an extra switch for the TV power cord. It  is switched off position every time the TV is turned off. It is not perfect, but it works.

Any other good suggestion is appreciated.

What happens if you disconnect the ‘other’ devices from the Samsung TV’s HDMI ports, leaving just the Arc connected?  Can you also just toggle off/on (and leave ‘on’) ‘TV Autoplay’ in the Sonos App ‘Settings/System/oArc Room Name]’ if the problem persists, then maybe change the HDMI cable between the TV and Arc speaker.

I tested the scenario with only TV and soundbar connected and  the Verizon box and Chromecast unplugged. The soundbar is disconnected from TV after TV is powered off.

I also played with “TV autoplay” in the App setting. SAme thing happens.

I am currently using HDMI cable provided by Sonos. I am ordering a high-quality HDMI cable from Amzon and I will try it out with the new cable and report the result.

https://www.amazon.com/gp/product/B08SM4212L/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&th=1

Could you not just try the HDMI cable that connects the TV to your Verizon box? (Just as a test?) just switch it over to your Arc and HDMI-ARC port? It might save you buying another cable at this stage.

My other thoughts are, it’s possibly the TV simply not ‘focusing’ on its Arc port - some older Samsung TV’s had a feature called Auto-HDMI-Switching/Detection and that used to cause problems with HDMI-ARC connected soundbars and that’s documented online with some models. So it might be an issue with the TV - maybe check it’s user manual for that Samsung feature as later they supplied an option in the TV settings to disable it. On earlier models it could not be disabled without opening up the TV (which of course is not recommended).

Here is an example website that mentions the auto-switching issue (just one of many articles on the topic) but I’m not entirely sure if it may affect your particular Samsung TV model…

https://www.theverge.com/circuitbreaker/2017/5/18/15658876/samsung-tv-2016-automatic-hdmi-switching-complaints

If the TV is affected by the Auto-HDMI-Switching then the easy answer would be to use the Sonos Optical-to-HDMI adapter and connect the soundbar to the TV’s optical port instead and setup the soundbar to work with the TV’s ‘remote’ using infrared. 

Thank you Ken for the suggestion.

After repeated testing the issue, I found that there was incorrect information in my previous report. I’d like to apologize to the community for the premature  information. The corrected bug reporting is as follows:

1. When  TV is only connected to soundbar, the soundbar stays connected after TV is powered off, then back on.
2. When TV is connected to soundbar and Chromecast, the soundbar stays connected after TV is powered off, then back on.
3. When Verizon set up box is connected  TV, the soundbar is disconnected after TV is powered off, then back on.
4. I tested 2 HDMI cables, it does not make difference.

I did not try to disconnect Verizon box earlier, because it is the source of the program and have to stay. Therefore the Verizon set up box is the trouble maker. It forces TV sound through TV build-in speaker. 

I followed following To disable CEC in the Verizon box...
Menu > Settings > Audio & Video > Video Settings > TV Input Control, press Disable.

It does not resolve the issue. 

I will try the optical cable next.

Any other comments/suggestions welcomed.

Have you contacted Verizon’s customer support?

Based on your testing, I’d guess that the CEC from that box isn’t actually turning off, and for some reason is, at some point, announcing itself as a CEC speaker sink, which the TV access and terminates the connection with the Sonos ‘sink’ connection.

There might also be value in checking the TV set for updates, too. 

A CEC-killer between Verizon and TV could be an option. 

@goldenpond,
Yes, as @106rallye suggests insert one of these between the TV and Verizon box and that should (hopefully) sort the issue.

https://www.amazon.co.uk/LINDY-HDMI-Less-Adapter-Female-Black/dp/B00DL48KVI

Problem solved:

I called Verizon technical support. Support instructed me to manually set up the Set up box to specifically works with Sonos soundbar. The problem solved.  If anybody has connection issues with a Verizon set up box, I recommend you to call Verizon support to solve the issue.