try one at a time and see if they work individually first. if they work individually, try starting with one device connected, play something with the Arc working and plug the other in to see if just plugging the device in causes it to stop. then swap the process with the other device playing and see what happens and report back.  TV, roku, and cable box model information will be useful as well as the current HDMI related settings on your TV.

I disconnected everything and plugged it back in one by one and it worked, as it did earlier and as it did yesterday. But when I turn the TV off throughout the day, it voids everything and the sonos goes mute. I did not experience this w optical connectivity. Somehow the sonos isn’t maintaining the CEC connection
 

I’m beyond frustrated. I’ve spent no less than 8 hours at this. I’ve talked to LG, Best Buy… I can barely get through to sonos and hv spent many hours trying. 

Sonos Arc
TV model LGSK8000PUA, size 65

cable Box Spectrum SMT – 84372

Roku 4200x

Any help you can provide would be greatly appreciated. I’ve been without TV sound all day! 

in any setup with a Sonos Home Theater product (Beam, Arc, Playbase, Playbar) the center of control is the TV. it is responsible for negotiating with and making sure the Audio and Video input streams make it to the right output.

in your situation, the LG 65SK8000PUA needs to be able to be in control and make it all work. the Sonos Arc is just connected to the ARC port for audio sent from the TV for the A/V source you select or apps you run on the TV itself.

if the problem begins when the TV is turned off and then back on but works ok when you connect devices to it after it has been on, my best guess is the HDMI initialization is not working correctly on the TV during power up.

since the power up sequence is where the problems begin i would try the same connection troubleshooting sequence: connect one device when the TV is off, turn it on and see if it causes the problem. then switch to the other device.

another thing to check is the firmware - make sure it’s up to date.

that TV doesn’t appear to have a lot of configuration options for HDMI but you could also try the same troubleshooting sequence above with the Settings>General>SIMPLINK (HDMI-CEC) setting on and then off to see if that changes any of the results.

another power startup related setting is the Settings>General>Quick Start+ option - try it on and off.

I have tried all those things and none of that is working. I have a migraine. I’ve been dealing with this all day! Called Sonos no less than 5 times, on hold over 30 minutes each time. I hung up. Tried Best Buy. Tried LG. Been troubleshooting on my own. No new product purchase should come with this much frustration and lack of customer support. This is beyond disappointing and still not fixed. I appreciate your help. I will wait in hopes others who have experienced this will comment with resolution. 

Hi @Kfran, sorry for the late response, thank you for reaching out and welcome to the community.

I would like to take a closer look at the diagnostics with your Sonos Arc.

One diagnostic will be from the Arc playing the TV audio and the other will be when it’s not.

Please reply with diagnostic confirmation numbers.

If you have other concerns, feel free to reach out.

What was the solution. I am having the exact same problem.

Hi @brentsavard, thank you for reaching out and welcome to the community.

Could you elaborate more on your situation, is the TV audio cutting out? is the Sonos soundbar not responding to the TV’s remote?

If you would as well take a diagnostic from the Sonos app and post your confirmation here. Setting > Help & Tips > Submit Diagnostic.

This will allow us to check for errors in the system.

I’ll be looking forward to your response.

Hi Kyle, 

Thanks for responding. The issue that I am having is that I have Telus Box attached into one HDMI and the Sonos Beam in the HDMI arc. When I initially set it up, it works but as soon as i turn off the the tv and turn in back on all the configurations are gone and the sonos does not work. I need to unplug TELUS, reset configuration for the tv to external speakers, plug back in Telus and it sorta works again. I was also unable to switch the sound from tv to music. I believe I need a CEC less adapter for my Telus box and I have since ordered one from amazon. I have also spoken to someone at Sonos who suggested I purchase the adapter. I have not ran a diagnostic because I have Sonos Beam and Amp boxed up to return it. If this new solution doesn’t work, not sure if I’ll stick around and keep it.  It’s been a drain on my relationship lol! 

Thx. 

I have had the same problem too… and there’s nothing to do with the TV and SONOS Arc. It’s just the cable box that not compatible with CEC. Eventually I have to connect the cable box to the TV with component cable instead of HDMI...

Hi @brentsavard, thank you for the update.

I understand the sentiment and thank you for your patience.

Troubleshooting what went wrong is never easy.

If you need further assistance, feel free to reach out.

Just wanted to get back to you regarding my issue. I ordered the CEC less adapter and everything is working as it should be with my Telus Box. Thanks for the support

 Thx. 

Brent

I have the same issue with a  2020 Samsung Frame. The ARC connection keeps breaking. Any more news on this?

There are a couple of threads in the Home Theater section of the Forum around issues with the Samsung frame. Last I recall, there was some discussion that Samsung was rolling out a firmware fix, but hadn’t yet released it everywhere yet. I have to admit not paying too much attention, as I don’t own a Samsung, but you may want to look for those threads. 

Having same issue with Sony XBR77A9G OLED set.  Sonos Playbar works fine but Sonos Arc constantly gives me issues.  Only solution is to disconnect power from TV for 10 seconds and power up again.  When it works with a earlier version Sonos product it seems to point to Sonos firmware to me.

Audio completely failed on my Panasonic TV when HDMI connected to my Sonos Beam despite hours of trying to work the problem out. The only way I have cured it is to use the digital audio to HDMI connection. One tip if doing this and you want to save yourself hours of frustration - remember to take the very small plastic cover off of the audio pin!!

Has Sonos come up with a solution to this?  I am having this same issue.  It is definitely not the tv because I tried it on our LG and our Sonos.  It is a bit disappointing that this issue has been going on for this long and Sonos has not fixed it.  

same issue here. just bought the Sonos Arc SL sound bar and every time i turn off the tv the sound bar gets disconnected.  turn the tv back on and the Sonos won’t connect.  I have to unplug the Spectrum cable box from the hdmi, connect the sonos and connect the cable box again.  I guess this sound bar is getting returned, i didn’t spend $800 bucks to deal with crap like this.  my crappy old samsung sound bar was $300 bucks and didn’t have any problems with the cable box. 

I bought this a few weeks back and it has fixed the issue.  Just hook it up to your hdmi cable  plug it into your cable box. https://www.amazon.com/gp/aw/d/B00DL48KVI?psc=1&ref=ppx_pop_mob_b_asin_title