@Myrdhin,
Perhaps it’s not your Android mobile and that you are looking in the wrong place to solve your issue …

You mention a WiFi access point, is that wired back to your main router, or is it a wireless WiFi extender? If it’s the latter, it might be that causing you the issue, as it maybe an unsupported type of network… see below list of unsupported networks:

• Wireless internet connections such as satellite, mobile hotspots, or LTE routers
• Guest networks or networks that use a portal login page
• Networks using wireless range extenders2
• Ethernet over Power (EOP) devices
• WPA/WPA2 Enterprise

Above list taken from the Sonos System Requirements HERE

I understand that the Sonos Controllers use SSDP multicasts (the UPnP discovery protocol) over UDP to discover the Sonos players. Both the Sonos players and controllers must share the same network subnet. However if the Sonos devices are connecting to multiple access points, the recommendations are that they be set to the same WiFi channel. This is for optimum performance particularly in groups. It appears some AP’s will work okay with Sonos, but others may not, particularly if the AP is perhaps auto-selecting their own WiFi channels and to solve any issues arising, many here (myself included) often suggest using SonosNet for Sonos device discovery/communication instead. 
 

Maybe just see if connecting all to your central router WiFi only solves your issue, by temporarily setting aside the WiFi access point …and if that works, then perhaps blacklist the players/controller device to not use the AP and see if that solves your issue.

Thanks but wifi is well configurated . I think SONOS should read all last bad comments in Google store about their ”app”

Once you insist it is X and not Y, you severely limit yourself from finding the correct answer to your problem.  Now, do you wish to fix your system, or simply whine about the app? 

I have just solved half the problem: my beam is recognized again.  The "super" and so "wonderful" SONOS app has just offered to update the firmware of the beam!  I confirm: the problem comes from SONOS and its app that it would be better to entrust to real developers

Beam firmware updated, had to reset my two one SL to link them again with the beam. All work... until the next SONOS app or firmwares update.

And there seems little doubt, in my humble opinion, that you will most probably encounter the exact same device ‘discovery’ issue again, going forward, because so far it seems as though you haven’t actually (yet) resolved the root cause. I guess only time will tell if that is indeed the case…

I have been professionally "dissecting" wifi for many years.  My network is correctly configured, I have no doubt about it. I'm working with all these protocols everydays.

What I'm also sure of, and I'm far from alone, is that SONOS had better focus on what it does best, which is hardware and sound, and  leave software development as well as third-party services (i.e. assistants, radio, etc) to those who already have much better experiences.

The app is just a remote to your speakers. If the app does not find the speakers, their probably something wrong with the connection of your system to your wifi. The fact other devices do not have any problems does not prove your wifi is problem free for a multiroom audio system.

The app is not only a remote, it's your SONOS "dashboard". Without it, you can't use your system.

If the app has some bugs and report to not see your speaker (perhaps because there is new app and firmware updates to support new voices commandes and resolve somes bugs?), the app guides you to a search for new devices, and/or a restart.  And if all that doesn't work, go to the doc which recommends a reset...

I have no issues with my Galaxy S20 FE. Have you installed a desktop controller? If so, does it play music without issues?

@buzz ì can not test now because I reset my Beam+2xOneSL.

Now I have a new problem  :

1. I see my Beam+2xOneSL (= Home Theater) in the App but not my 2 SONOS Roam…
2. I keep my 2 SONOS Roam ON and kill the app. I restart the app : I see my 2 SONOS Roam but not my Beam+2xOneSL anymore 
3. I turn OFF my 2 SONOS Roam and… My Beam+2xOneSL is back and my 2 SONOS Roam disappear
4. If I turn ON my 2 SONOS Roam, they don't appear in the app

Is it the wifi  ? Sorry but we know it’s a bug in the app!

Submit a diagnostic and post here and somebody from Sonos will hopefully come along and see it.

My guess is you have a kind of WiFi mesh system and some speakers are connected to one part and others to another. Within your own network they appear fine but your phone maybe only sees the ones that is is currently connected to.

@sjw Thanks. But no mesh and only one access point where all my device (with each an different IP) are on.

So you have an Access Point - which is a way of achieving what I described.  If you submit a diagnostic Sonos will see which devices are connected where.

I do think some work needs to happen on this kind of setup personally as AP’s and mesh systems are much more common now than they were not too long ago.

Supposedly even being on different channels can cause issues, never mind being connected on the same IP address range but one served by 2.4GHz and the other by 5GHz.

The user (for me) should not need to concern themselves about this - if they’re all on, for example, 192.168.1.XX then they ‘should’ work.

I’m sure ‘work’ may be involved from Sonos and other networking equipment manufacturers - but solving this would be in everyone’s interest - especially the users’.

Thanks @sjw I totally agree with you. I’m working in the WIFI “domain” and I know (I hope ) how all this hardware and protocols works.

No mesh at home today and all my SONOS devices are connected to 2.4GHz. My phone is on the 5Ghz, yes, but, like you say, that shouldn't be a problem : the discover process appear to “broadcast” on the 2 “types” (2 and 5GHz). And like I describe it, sometimes one appear, sometimes it’s the other despite my phone is always on the same wifi freq.

I tried to contact SONOS but as usual, nobody available…

I seem to remember having read in the last few days in this forum a concern similar to mine and that apparently, SONOS was aware of the problem of this user, that it was a bug on which they are working...

An interesting thing that I just discovered: when my 2 SONOS Roams are found (but not my “Beam2+2xOneSL”), I have my music list "My SONOS" and my playlists in the app. However, when my”Beam+2xOneSL” is found , the music list "My SONOS" is empty and my playlists have disappeared.

I have open another discussion because I think it’s not the same thing. the link : 

Do not Factory Reset any SONOS units without further consult.

That said, have you Factory Reset any units while you have been working on this problem? I suspect that you have and this can help explain the disappearing playlists.

@Myrdhin,

It sounds to me like the setup has been ‘split’ into two different Sonos Households within the same Sonos account & App and I agree with @buzz to not factory reset anything at this stage as you may end up losing the main system along with all the services, playlists and settings. I would see if the Sonos Support Staff will perhaps check the setup you have and then take things from there.

Since you did a factory reset of your home theatre room speakers, it’s entirely possible that you set them up as a separate household, essentially a separate Sonos system.  That would explain why you can connect to one system (home theatre) or the other (Roams) but not both at the same time, and why playlist appear periodically. Obviously, can’t see into your system and confirm.

I understand that you believe that your issues are a bug in the android app, but that seems highly unlikely since the evidence points to issues with how your system is setup.  Typically when bugs occur in the app or the speaker firmware, we are going to see a lot more complaints about, particularly when it causes systems to be pretty much inoperable.  Possible that the bug only occurs with your situation, which doesn’t appear to be that unique, but not likely.  The vast majority of issues like this are doing to network or setup issues, and it’s quite common for people to believe that it’s not their network or setup.

You’re better off posting a diagnostic here for Sonos staff to look at, or contacting Sonos directly once they are available. 

Try to post a diagnostic while the ROAM’s are visible and another while the surround Room is visible.

Again, don’t Factory Reset anything at this point.

Thank you very much for your attempts to help.

Before reset I tried all the methods (OFF/ON, search devices, reboot router , etc). I read a lot of posts here…

I've had SONOS for a few years now and the more time passes, the more I see the quality drop. I disassembled some (old models) to see what was inside. I isolated systems to listen and analyze the different network frames and protocols used. To be honest, I'm afraid of the new hardware that will soon be. The Roams are far from being of good quality (problems with battery, connection, sound...). The Android application is very far from being ergonomic. I also really like the steps to try to find your system, steps that end with "let's try again later..." rather than sending a report to support with a request for comment, for example.

I solved my problem last night and I confirm: there is a problem during the exchange of frames allowing the discovery of other elements of a system. But when I see the answers of some knowing people, I prefer to avoid making them lose the illusion that SONOS is a bug-free system .

Thanks again,

If you elaborate on your findings maybe you could help Sonos.