Since the current version of S1 is 11.2.6, I assume you are on S2.  The current version of S2 is 13.4, so the first thing I would do is upgrade then retest.  No point in doing anything else before that.

Not sure if you’re up to date with Plex.

The OP has Play:5/gen1. 

Then if on S1, I don’t know how OP is on version 11.2.13.

https://support.sonos.com/s/article/4941?language=en_US

That page is well out of date. The latest downloads for S1 are 11.2.13.

It's definitely 11.2.13. Yes, I'm stuck on S1 for now as I've got a couple of legacy devices. Don't think that's the issue though, as it's been working fine previously.

Plex version is the latest.

I think the Plex issue maybe known to Sonos already, as there was a ticket open for investigation a short time ago. I’m basing that comment on this thread …

I’m still seeing the issue too from time to time with my Plex server and plex-pass.

This was a separate issue that was resolved as far as I’m aware. There’s a thread on the Plex forum about it - seemed to be that Sonos’ Plex integration was passing a malformed request string to the Plex API which is now fixed. I’ve not seen this for a few weeks now. https://forums.plex.tv/t/unable-to-browse-music-using-sonos-with-pms-1-24-1-4931/740590

Quick update on this…

Spent over an hour on the phone with Sonos support, who basically went through same troubleshooting steps I had. Very thorough and helpful but unfortunately couldn’t identify any issues their end and suggested it might be a ‘Plex account issue’. (Not entirely sure what that means!)

Anyway, checked out the Plex logs again and there’s a couple of messages related to TLS:

CERT: incomplete TLS handshake from <my router IP> no shared cipher

Based on this, in Plex, I changed the TLS setting from ‘Preferred’ to ‘Disabled’, and boom, I can play music again!

There’s also an option in Plex ‘Strict TLS’ which forces only the most secure ciphers, etc. This seemed to have no effect.

I haven’t solved this fully, so need to investigate further, but my suspicion is that Sonos is using an older TLS cipher that’s been deprecated in the latest Plex version.

Will update again when I find out more.

Oh, one other issue - although I can now play music by disabling TLS (which I don’t want to do long term), the dreaded ‘Unable to browse music’ error has reappeared!

Addendum to my previous - I don’t actually have TLS set up on this setup, so not sure why my TLS was ‘preferred anyway’. Still, it’s another avenue to investigate when I get time.

Starting this morning after Plex updated to v1.25.3.5385 I’ve started to have exactly the same “incomplete TLS handshake” message appear in the logs when trying to play anything from plex with Sonos. I have the same version of Sonos, 11.2.13 S1 and I can’t upgrade to S2 because I still have a Play5 (Gen 1).

Was anyone able to find a solution that did not involve disabling TLS in plex?

FYI supported TLS ciphers that Sonos support are here: https://developer.sonos.com/build/content-service-get-started/security/

Updated Plex to 1.25.3.5409 today, but still the same issue.

@controlav - That doesn’t help because I have no control over the ciphers that the Plex integration within Sonos is using. I’ve posted this on the Plex forum as well to see if they can provide any assistance. It’s unclear to me whether the problem is on the Sonos or the Plex side.

https://forums.plex.tv/t/sonos-incomplete-tls-handshake-no-shared-cipher/770461

(Following this on both forums too)

It appears that the beta of Plex (post 1.25.3.5409, and so presumably the next release) removes the option to disable TLS so this will not be a workaround for much longer. (Also, disabling TLS prevents use of the Plex web app, app.plex.tv, from outside the home network).

My guess would be that Plex no longer supports whatever TLS ciphers are used by Sonos. I don’t know the full list of ciphers supported by Plex, but I suspect they’d be loathe to reintroduce any legacy ciphers that have presumably been depracated for security reasons. Therefore, I think the question is will Sonos update v1 of the app to support more modern ciphers supported by Plex? I think this falls into the ‘security and bugfix’ category rather than new features so hopefully it will be looked at.

Errors during playback have nothing to do with the app: its the speakers that reach out to the Plex service. I already posted the list of supported ciphers. I don’t believe that list is different between S1 and S2. You need to ask Plex what is going on.

This problem has existed for months. No-one at Sonos or Plex appears to care:

https://forums.plex.tv/t/sonos-playback-from-remote-plex-server-fails/738181

Hi @timmyc 

Would you please submit a diagnostic and reply here with the number given immediately after recreating this issue? Thanks. 

Thanks for taking a look at this.

Here’s a diagnostic from my S1 system, connecting to a remote Plex server: 517105511

This diagnostic is taken just after a search in Plex for an album (successful), followed by three unsuccessful attempts to play a track from the album with the error message: “Unable to play 'Breakwater House' - the connection to Plex was lost.”

Exact same  issue/error message for me too @pwt 

Diagnostic: 380152644

I have plex pass and have forwarded TCP port 32400, using UPnP (and have tried the port manually forwarded too). The online server access/share is confirmed on the Plex server as working and has the green check-mark.

The Plex server software is bang up-to-date on the NAS .

The native Plex App works absolutely fine for me both locally and remotely and finds all my Sonos products on the LAN. I can ‘connect’ to a Sonos room and play tracks from my plex server library with no issues at all from the Plex app itself.

The same NAS (plex) library is accessible locally too as a Sonos (SMB) library aswell and that sharing method works fine via a Sonos App Library share. 

I can goto a track/album in the Plex native App and play it on a Sonos Room and see the track/Album in the Sonos App room queue and all plays fine, but as soon as I go via the in-built Plex service in the Sonos App (even selecting the same track/album) I always get the error message ‘the connection to Plex was lost’. I can browse the Albums and on selection the Album tracks will even all load to the chosen room queue but then it just doesn’t play.

Researching online has led me to think the issue is possibly related to my router in my own case, which is ‘Plume WiFi’ and the suggestion from others, is that my router does not support ‘NAT Loopback’ and that is blocking the Sonos service from working. I just haven’t been able to confirm this with anyone. Nor can I find a way (yet) to resolve the matter.

A passing observation: Unless the Plume is in bridge mode you’ll be in double NAT, assuming there’s an ISP router. Forwarding inbound traffic therefore wouldn’t work, at least without jumping through some extra hoops.

The ISP supplied router is in ‘modem mode’. So no bridge/double-NAT.

Others online have suggested to me to actually bridge the Plume pods as Wifi access points and switch back to using the ISP router instead, which is a VM Hub-6ax and should support NAT loopback (perhaps). It appears others have had success with this, but I prefer to stick with the Plume service at the moment because of other things that their service provides - I can still use the Plex service with Sonos through the native Plex App - it’s only the Sonos in-built plex service that does not work for me.

I think I’m just going to have to live with the issue, but would be nice if Sonos/Plume could resolve the matter and allow the service to work in the same/similar way as the Plex App itself. I have written to Plume Support too in the (now-distant) past.

Hi @pwt and @Ken_Griffiths 

Thanks for those diagnostics - I’ve forwarded them to our engineers who will investigate the issue.

We are unable to reproduce this issue. This is good for other users, but it makes it harder for us to help you all here.

@Ken_Griffiths - I’m told you have a different issue than the others - no NAT Loopback will prevent Plex from working.

@pwt & @timmyc - Could you please let me know your current Plex server network settings? Thanks.

Thanks.

Did you test access from an S1 system to an external Plex server, i.e., one on a different network to the Sonos system? I have no issues when my Sonos systems are on the same network, with either S1 or S2.

Note also that all the native Plex clients connect without problems when remote.

I’ve attached the network and remote access settings as screenshots below. I have port 32400 on my router forwarded to the Plex server.

Now, looking at the ‘Strict TLS configuration’ setting (an option I don’t remember seeing in the past), I’m wondering whether relaxing this would fix the problem. Unfortunately, I can’t test it at the moment.

Hi @pwt 

Thanks for that. Yes, we tested a speaker on a mobile hotspot connecting via LTE to the Plex server. Our Plex settings match yours, and Strict TLS doesn’t appear to make any difference.

Are you running the native Plex server, or on a Docker Container?