Did you connect your Sonos One to the primary node of the router?

Been too long since I fooled with Sonos on a mesh setup but I recall several requirements like all APs using the same SSID and being on the same channel. Can’t find a FAQ on that though, maybe search past posts?

Sonos can work well with mesh systems, and putting those speakers that can connect to SonosNet is often a big part of the solution.  It may require particular approaches or settings, as alluded to by @Stanley_4 , but it is usually possible to get things working fine, even with a Move or Roam involved.

@SteveC_4 - when you tried SonosNet, in what way did the Roam fail to connect / work?

Make sure you are fully up to date on BT firmware, as there have been recent issues with communications between to the two wireless bands on BT, which I think BT has now addressed.

I think Stanley wants to refer to this FAQ. It’s indeed confirmed that Move and Roam do not support SonosNet. Maybe this is because they are intended to serve another purpose: to be movable and used (with BlueTooth) in areas out-of-reach of the SonosNet ...

That is part of the reason. Also, every time you moved - or removed - the portable speaker, SonosNet would have to reconfigure. Permanent speakers may be getting their signal via a portable one, which is undesirable. 

There are clearly pros and cons for not allowing Move and Roam to connect to SonosNet.  It certainly isn't a 'bizarre' decision. 

Yes - it’s connected to the primary node and to the question from @John B, all BT firmware is current.

What happens with the Roam is that it still connects to WiFi rather than SonosNet - the absence of this support for Roam and Move is confirmed by Sonos as @el rubio notes.   Very strange decision by Sonos.

Putting all the non-portable devices onto SonosNet does actually improve the situation as now everything except the Roam works correctly and I’m only having to deal with one device occasionally disappearing from the app - and I don’t often use the Roam when at home anyway.   The Roam does have one very useful feature at home though as you can use it as a sort of Bluetooth gateway to get around Sonos’ lack of Bluetooth support on the non-portable devices,  Once streaming to Roam vis Bluetooth, the app can be used to group this with other Sonos speakers.

Looking at the overall issue with mesh networks more closely, it seems to be a problem with the Sonos app, rather than the devices actually losing WiFi connection.  If I look at the status of the speakers on the WiFi router/discs then all Sonos devices show that they have a valid connection to the network and I can stream to them from my phone using (for example) the Spotify app.  The problem only occurs when trying to do anything with the Sonos app - various devices disappear from the list in the mobile app as the phone is moved around the house, and sometimes re-appear after 10-20 minutes - or in the worst case after re-booting the missing speakers.   So this seems to be a mesh related bug in the Sonos app - all devices are on WiFi, and can be seen by other apps on the same phone (Spotify for example) - they just can’t be accessed from Sonos own app !

It cannot be a 'mesh related bug in the Sonos app'. The app is just a remote control for the system. 

One possibility is the connection flipping between the two WiFi bands. You could check that by experimentally turning off the 5GHz band on your network.  (I am not saying it's definitely that, just a possibility.)

Or if the BT network has 'band steering' or QoS you could try disabling those.

A potential issue with using Sonos on WiFi meshes is the fact that such systems frequently deny the user any control over wireless channel allocations. Some also prevent the user from splitting the 2.4 and 5GHz bands onto different SSIDs, enforcing band steering.

All these ‘helpful’ aspects are find and dandy for those who want to fit-and-forget, and only use devices which connect out to the internet. Sonos is a complex system which relies heavily on inter-device communication, both for controller access and between players. It performs optimally in groups when all the devices share the same channel, as it can then communicate directly peer-to-peer. When a WiFi mesh intrudes, such inter-device communication may have to take the long route round, via meshed access points and mesh backhauls.

As for the ‘strange decision’ by Sonos to limit portable players to WiFi, the impact of inserting a mobile node into the SonosNet mesh has already been touched on. Basically the mesh would have to keep recalculating itself. There would be frequent Topology Change Notification floods, which could upset playback in the rest of the system.

I suppose in theory Sonos could have made the portable players behave like the old CR100/200 controllers, attached as branches off the mesh but not acting as repeaters, but they stripped out all that legacy code years ago (from S2), for good reasons one would imagine. Besides, why (re)introduce an old wireless technology into what are modern devices able to make use of 5GHz WiFi?

I’ve looked into the things like the phone connection flipping between bands etc. and disabling 5GHz doesn’t help.

What points me towards the app is the fact that from the same phone, I can always see all of my Sonos devices from within the Spotify app via Spotify Connect, but if I then switch to the Sonos app, some devices are missing.  If there were any connectivity issues on the phone related to 5GHz, QoS etc. then these would also affect the Spotify app - but I’m only seeing the issues in the Sonos app itself (latest version of S2).  Other control mechanisms such as Google Assistant and Home Assistant also work fine on the mesh, it’s just the Sonos app that sees devices disappearing.

One way round this would be to not use the Sonos app at all, but that would remove access to things like playing music from a local NAS and all the multi-room functionality.

While yes - the app is just a remote control, that doesn’t mean that it can’t have problems with the way that it does device discovery, for example.   When a phone is brought back into a house after being away and out of WiFi range, there is often a delay before it finds everything, and one possible explanation might be that it is repeating this discovery process every time it moves from one mesh node to another - and also taking a VERY long time to carry out this process.    Other apps on the phone seem to do this in a different (and more efficient) way.

Thanks - that does seem like a good probable reason for them omitting SonosNet on Move/Roam.

At least having all my other devices on the Sonos private network does seem to have solved most of the problems.

As you mention, the discovery process could well be different. Some applications may use a cloud-based discovery (they ask a remote server, which already has a list of pre-registered devices).

The Sonos controller discovers devices locally using SSDP (a standard UPnP protocol), which in this case runs over both IP multicast and local subnet broadcast. It’s not unknown for some network equipment to refuse to forward such traffic correctly between WiFi bands, and between WiFi and other network segments. 

One also shouldn’t rule out the mobile (phone/tablet) itself, since some can end up with a misconfigured network interface.