Try changing your router to use a ‘fixed’ non-overlapping WiFi channel. Use either 1, 6 or 11 and set the channel-width to 20MHz. Also see these three links:

Change Router Channel

https://support.sonos.com/s/article/4769

Wireless Interference Document:

WiFi Interference

Wireless Interference Video:

Wireless Interference and Sonos

Thanks for the quick reply Ken. 
 

I’ll give it a shot and report back. I believe I should be able to change the Wi-Fi channel, but don’t think I can change the wifi channel width on my particular mesh system.

I’ll also try using the ISP router network, which I’m sure I can change those settings. 
 

Thank you very much

As you are using a wifi ‘mesh’ system, it can sometimes be better (in some cases) to wire a single Sonos device to the primary hub/router, as that then switches ALL Sonos products to run on their SonosNet signal instead and you can set that to a fixed channel in the Sonos App network settings.

So, if that’s practicable, you could also try that if you still run into any issues.

Just to add I wouldn’t use your ISP router WiFi alongside your mesh setup - it’s usually best to leave that particular WiFi switched off and leave the device in bridged mode (or acting as a modem only).  

Thanks once again for your help Ken.

I checked my mesh router settings and unfortunately the options I can change are quite limited, so I couldnt’t test the solution you posted earlier. I’ll eventually replace it with something more advanced. 

So instead I’ve tried reseting both devices to factory settings (press and hold the play button whilst plugging them in until it flashes green) and set up a new system from scratch with one of them being plugged in by Ethernet. It was not possible to keep one plugged one directly to the main router, as the router is not near any of the speakers, so instead I’ve plugged it into one of the ethernet ports of the mesh node.

I’ve set up the first one using ethernet, which went smoothly. When setting up the 2nd one, it didn’t ask me for any wifi credentials, meaning it connected via the Sonos network.

I’ll give it a try like this and report back later.

Thanks once again.

I’d like to give an update on this problem.

Last weekend I set up a new system from scratch with 1 speaker connected by Ethernet, whilst the other is connected using the SonosNet. Neither speaker have WiFi credentials saved, so it’s not possible for either to use my home WiFi network.

Everything was working fine until this morning. This morning I noticed that the speaker connected by Ethernet dropped, showing neither on the Sonos app, nor on Spotify. Strangely enough, the second speaker (which is connected using SonosNet through the first one) is showing and working as normal (used Spotify connect and it played just fine).

Is it normal for a speaker to drop but still being able to bridge the others as normal? If anything, I’d expect the 2nd speaker to drop and the one connected by Ethernet to keep showing.

I have sent a system log to Sonos (using the Sonos app), so if an engineer is able to take a look, the ID number is 1917392732.

Thank you very much in advance for your help.

It’s more likely a "discovery" issue - Sonos uses SSDP (multicasting) over UDP for device discovery and it’s possible that if your controller device is connected to one access point and the speaker is connected to another access point the discovery may ‘occasionally’ not complete correctly, particularly if the access points are operating on different channels - if it happens again simply try toggling off/on your mobile devices WiFi network connection. Even though the App is not seeing the speaker it "most likely" is still connected to the LAN and is working okay.

Some users with iOS devices as their controllers may also occasionally see issues like this because of iOS security including the use of ‘Private Address’ MAC spoofing in the WiFi network connection settings with some routers/access points, so perhaps see if switching that off helps at all. It’s not needed for Home based wireless networks anyway.

Sometimes a reboot of the WiFi Access point(s) in use can also quickly resolve the issue.

Thank you for your quick response Ken.

Only to make sure I understood you correctly. If my iPhone is not connected to the same mesh node as to where the speaker is plugged in, the speaker may not show?

I have just tried the following steps:

I have set my phone to airplane mode for some time (about 20 seconds) and disable it next to mesh node (to ensure it connects to the same node as the sepaker) and unfortunately, the speaker still did not show. I have then decided to check the TP Link app and it only listed one speaker as being connected. Unfortunately, as both have the same name (SonosZP), I can’t tell which one that is.

Afterwards, as suggested, I tried rebooting my access point, and afterwards no speaker would show. Only after rebooting the main speaker, has it began to show again, but not the secondary speaker (most likely because it has lost connection to the main one and still has not had the chance to reconnect).

I have had the Mac address spoofing disabled for some time already (was tired of the router notifying me of a “new” device every day).

I really hoped this was a simple solution, but it appears it’s something more complex. As the issue become more pronnounced since the last firmware update on the speakers, is there any way to downgrade to the previous verion? At least to rule out any botched software update (although I expect the speakers verify the integrity of the update before installing it)

Thank you very much for your patience and help!

There’s no way to downgrade, as far as I am aware, you would need to see if the next update fixes things. Although just to add I have a mesh setup here too and not seeing any issues (so far) with the last update. Can I just perhaps clarify a couple of things…

1. Is the wired speaker connected to the ‘primary’ mesh hub rather than a ‘secondary’ satellite hub?
2. Have you tried a different SonosNet channel in ‘Settings/System/Nerwork’?

Thanks for the swift response!

The speaker that is wired in is connected to one of the satellites of the mesh system which in turn is connected wirelessly to the other 2 nodes (the primary and another satellite) that are both wired in to the ISP router (which is handling DHCP). Unfortunately I don’t have a way to wire in that last satellite. The primary hub is sitting next to the ISP router at the entry hall. The secondary speaker is physically closer to the main hub, but not in a way that makes it feasible to have it wired. 
SonosNet channel was set to 11, and I just switched it to 6, hoping it will help! 
 

Thanks!

Ideally, the wired Sonos device should be to the primary mesh hub only, as that reduces backhaul and the involvement of a wireless connection between the primary and satellite hub. I know some use a Sonos Boost in the situation where they cannot easily wire a speaker, but I would see how it goes rather than do that and even try the setup on your mesh WiFi signal again, perhaps? - if you do that however, then please don’t forget to add your WiFi credentials back to the system via “Settings/System/Network/Manage Networks/Update Networks”.

I meant to also mention here in the thread that It’s also often helpful to reserve the Sonos products IP addresses in the local DHCP servers reservation table when you have the system back up and running correctly. 

Thanks for the quick response Ken.

I have decided to try the following apporach for testing:

I have moved the main speaker to the office, where it is now sitting on the floor next to the mesh sattelite and wired in (the mesh sattelite is directly wired in to the ISP router). The secondary speaker was moved to where the previous one was and is connected wirelessly using SonosNet. Right now both are showing up on the Sonos app, on the TP-Link app and on the Spotify app on my iPhone (both as a Spotify connect and AirPlay device).

Reckon this would be a good approach to isolate any potential issues with the speakers?

Thanks!