Unfortunately, the details of your setup and the issues you are encountering are not sufficient to offer any assistance. I understand when technology doesn’t ‘just work’ it can be frustrating, but we need more specifics in order to offer any help. 

I have two beams both have been experiencing intermittent sound which has got gradually worse until now the TVs they are connected too do not show up in the app...and if they do suddenly appear the sound is intermittent ...today As I was watching the TV icon in the app dissapeared I have read and followed guides that have been suggested as others have put this up before me I've purchased new hdmi cables to no avail.

The TV doesn't show in the app at all. Thei Beam does. Or are you referring to the audio sources for the Beam?

Hi...both beams are connected by optical cable both beams are active and live as are the two ports but the TVs dissapears from the app selection for no apparent reason...then switching on off one comes back but the sound is intermitant ...then it will play ok half an hour later...then the sound will fade it's all over the place...this afternoon neither TV was detected...tonight one has suddenly appeared in the app and is giving sound but patchy .. I have swapped out hdmi cables and have more arriving but it is the app that appears to be unhappy.

So, as John suggests, the Beam is disappearing from your controller application? The TV itself would never show up, the Beam should.

It might be worth trying a network refresh, by unplugging all Sonos devices from power, then perform a reboot of your router. There is no need to disconnect the HDMI cable / optical cable between the TV and the Beam, just the power cord on the Beams. Once the router comes back up, plug back in all Sonos devices. 

I think that would clean up the fact that the Beams are not showing in the app. Then, I would double check the audio settings on both TVs, and make sure that they are both set to send only a Dolby Digital signal out. Not “Auto”, not “Best Available’”, not “Dolby Digital Plus”, nor “Atmos”.

If you continue running in to trouble, it may be worth it if you were to submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it, or post the diagnostic number here for a Community Moderator to pick up.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the phone folks, there are more options available beyond just the diagnostic analysis.

Yes I will have to try that...don't you have to be invited to send a diagnostic, thank you, Phil.

Turned everything off overnight reset internet turned on Sonos equipment one by one both TV show in New app but with no sound which it used to, I had previously run the optical cable from an Android TV box with no problem so I switched the cable to the optical out of the TV and activated CEC and set output as pcm and it's now all up and running ..it had always run fine before but obviously the new app needed the configuration to be different and both beams appear in the app and can be adjusted easily which they had stopped doing....

Hi.  Your post makes no sense whatsoever, but if things are now working let’s just n=be grateful for that.

Well it doesn't make sense that it stopped working for no apparent reason...here is a screenshot of the app and both TV/beam appear and work perfectly which had not happened before it was very hit and miss...

Lardybarstow, 

Maybe try this - switch off HDMI-CEC on your TV and also disable CEC on any connected TV boxes (if that’s possible) - leave the Beam connected to the TV’s optical port using the Sonos adapter provided and then see how it goes after that.

Note; you may need to set the TV sound-out back to optical after you have switched off HDMI-CEC.

Thanks Ken all seems to be well now and I'm able to switch the app seamlessly between devices and rooms it just seems the app no longer liked my original set up but it now seems spot on thank you.

Ah good to hear, Maybe see how it goes and if you encounter any further issues with your Sonos system, then maybe pop back here.

It's been a couple of days since my anti Sonos rant .....I've been a bit petulant on here...like many we have lost  our livelihood during covid and my partner has lost everything home business and now health with cancer having just had a double mastectomy and undergoing treatment that really her health can not tolerate ...I took out my frustration on this forum and Sonos products which if I had of just researched better and not had a hissy would have just worked out and needed re- setting and a bit of time....highly embarrassing as our Sonos system is spot on and provides much in sound and comfort in all areas of the flat...to all those who may have read this post I apologise for my petulent tone and manner.....wishing you all a safe new year ...Phil.

No worries at all Phil, it sounds like you and your partner are going through a rather distressing time and I truly hope that the New Year brings you both Health, Wealth and plenty of Happiness. Stay Safe.