I had the same thing happen yesterday. Same TV too. There was a software update the other day so I might be to do with that. I set my audio to auto instead of pass through and still get Atmos on Atmos content on Netflix so that is ok. I do suspect I might have to put it back to pass through when using my Blu-ray player though. 

Oh and it's not just iPlayer. It affects all the UK TV catch-up sites as I checked them all. So iPlayer, ITVX, 4 and 5 are all affected.

All other apps like YouTube are fine 

I have a Beam 2 by the way.

Hi Sarah thanks for your reply! I’ve just checked my other apps and they all seem to be playing in multichannel pcm 2.0 when pass through is on, but iPlayer playing nothing. 
 

I didn’t realise there was a software update the other day, you do mean Sonos right? As my tv hasn’t had one.

Hopefully this can be sorted soon one thing after another recently with this system.

No I was my TV that did an update on Weds as when I switched it on, it said it had done one. From then, I had no sound from all the UK catchup apps. It was only last night that I fiddled with the settings and took off passthrough, and set it to auto. Then I got sound on ITVX again. I then left it on auto, and watched something on Netflix in Atmos, and it did play in Atmos so I’m guessing the auto setting will enable the correct output from the TV apps at least - so hoping it works likes it did when set to passthrough. My only issue might be my bluray player, so I will need to test that. 

Update was = 03.40.70 I think so check your TV

Yeah I’m on that firmware now and I’ve had automatic updates turned off so not sure why that’s happened  

let me know if you have the issue with the blu ray player!

im not really sure where we go from here as it seems LG have messed something up and not Sonos ffs :/

I will test out the bluray player and let you know. Yeah I think this is an LG issue and not Sonos which is a pain. As all my TV apps seem ok with the setting changed to Auto, it might be a case of switching it back to passthrough if I use the bluray player (assuming the auto messes it up). Luckily I don’t use the bluray player that much really.

I don’t want to have to change the setting every time I switch between iPlayer and my ps5, which is a lot as my little one wants Bing on iPlayer all the time :/ 

I have this exact same issue - I have noticed some changes after LG’s latest update on my A1 OLED (03.40.70). I have a Beam Gen 2 and 2x Sonos One’s in a 5.0 set up through eARC with my TV audio output set to ‘Pass-Through’. Since the update I lost audio on BBC iPlayer and ITV Hub. In the Sonos app I now have ‘Unsupported TV Audio’. What I had to do was switch my audio output to ‘Auto’ so that it would auto switch to PCM audio I guess when needed. Just feel like I’m now not getting the best overall sound quality as I am now getting ‘PCM multi-channel’ on inputs where I used to get Dolby Digital. This is resolved by changing back to pass-through but I don’t really want to have to keep changing back and forth whenever I use certain built in apps. Also, if I leave Pass-through on but turn off eARC this resolves the issues but then leaves me without Dolby Atmos ability on other apps! All worked fine on Pass-through + eARC before update.

Basically its broken the eARC functionality.

I believe this is the LG update that has caused this. For now I have switched to the ‘Auto’ audio output which ‘sorts’ the issue but means I get some multichannel PCM on Freesat channels when I would prefer Dolby Digital. As with my PS5 - There has been an update now where you can activate Dolby Atmos on the system. This means the PS5 kicks in with this fine on the Auto setting. Have raised a repair with LG to see if they can roll back my software.

You can now switch the PS5 to Dolby Atmos output in the Playstation Sound settings. That arrived in an update not long ago. Should save switching each time.

I’ve been using that setting within the ps5 but for some reason it keeps changing itself back to linear PCM this not transmitting atmos to the soundbar, I’ve just changed it back now and atmos is playing with the pass through on the tv setting is set to auto which is good, but I don’t understand why that setting keeps changing, maybe something to do with the fact that I’ve been switching remote play  and the tv a lot recently ? I don’t know. 
 

Under the same settings itv plays under Dolby multichannel pcm 2.0 and bbc iPlayer is playing as stereo PCM. It seems now my kodi wants to play at Dolby multichannel pcm 2.0 so going to have to mess around with them settings when I get time, nightmare this is

Also having this update on my A1 OLED since the 03.40.70 update

I’ve just emailed LG, I imagine the more people that do it the better chance we have of fixing this problem: 

https://www.lg.com/uk/support/contact-us/email-us/

Same issue here after my LG TV had a system update. I have also emailed LG customer support about the problem and expressing my frustration that it happened to us on Christmas Eve!

Got a reply from LG, most relevant part below:

I want to assure you that your feedback has not gone unnoticed, and we understand the inconvenience this situation has caused. We've received numerous emails from valued customers like yourself, all highlighting a similar experience with the audio output when using the eARC HDMI set to pass-through mode on the TV.

After a thorough investigation, it has been identified that the issue is indeed related to the latest software update. Please know that our headquarters is fully aware of this matter, and our dedicated team is actively working to develop a comprehensive solution. We understand the importance of a seamless audio experience, and we are committed to resolving this matter promptly.

That is great there has been an acknowledgement. Hopefully another update soon then. I just had a call from LG to just say they can't roll back software on TVs as expected and to “use another HDMI cable” as the TV is out of warranty.  

My work around at the moment is to leave pass-through on and turn off eARC in the menu. Seems to then work on built in apps on passthrough mode and Atmos still works on normal ARC mode when required.

I think the most important lesson here is to disable auto-updates for your TV firmware: if it ain’t broke, don’t let LG try and fix it.

Disable auto-updates pretty much everywhere.

Check the tech news and forums to see if all is going well with the early updaters. Wait until you have time to fuss if something glitches. Then update.

I’ll admit to not doing that for Sonos as they haven’t broken anything for me for a long time and if it does break I’d want to post about it here.

Hey I’ve just seen this thank you for sharing , though unfortunately no updates as of yet though on my TV

LG released a firmware update on 8 Feb version # 03.40.80. Auto update didn’t find the update so I downloaded and installed it manually. Unfortunately, for me at least, it hasn’t fixed the no audio when set to pass through problem on iPlayer for the apps on my LG B1. I’m connected to a Beam 2, 2x Sonos Ones, Sub.

Auto Update found the same 03.40.80 update today but it did not fix the issue for me either. LG A1 connected to Sonos Beam Gen 2 + 2 Ones.

Yeah I’ve had the same this morning and it’s not fixed it either, doing my head in now