Might be worth it if you were to submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. I’d think Sonos could possibly ‘see’ the reason why this pop up is occurring, and give you better hard suggestions than those made by us here in the forums.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.

thanks so much for that advice.  Will do!

so after submitting a diagnostic it appears my wifi router is generating two hidden networks other than my normal 2.4 and 5 GHz ones and Sonos is thinking they are range extenders.  Makes no difference…  all works  fine.. just annoying the message pops up to warn me.  Will have to figure out why my router is doing that! 

thanks again for the advice

Glad they were able to see something that none of us would have ever guessed. 

I think my next step would be to contact the CS of your router, and ask them what is going on :)

Are you using the default SSID (user name) and password from your ISP’s Gateway? If so, it’s possible that they all use the same SSID and password by default. This would be silly and awkward, but possible. You could try changing the 2.4GHz and 5GHz bands SSID -- and you’d also need to change these in all of your devices.

A better plan would be do disable the extra connections -- if you can figure out how to do this.

yes, that is the plan! thank you. lets see if i find a way ..

@fnegrin One other thing you might try, even if just experimentally, would be to connect one of your devices by Ethernrt to your router, so as to trigger SonosNet. Then remove your WiFi details from Sonos in Settings, System, Network, Manage Networks. This might stop the Sonos system from looking for any WiFi network and hence throwing the error. 

That's a bit speculative though!

Yes, thank you!  indeed I thought of trying that …..  But I would need to go buy a veeeery long ethernet cable or temporarily place one of my speakers near the router in a place I could never actually keep it , just for the test.   Would be interesting  but maybe not worth it and easier to click on “ok” when the little message appears! 

Fair enough. I think it would eventually really irritate me. But then I am very easily irritated!

I like the suggestion from @buzz to change the SSID on your router if it is still the original at the moment.  But that may not be worth the effort either.

Update:    my wifi router, like most do, emits a 5GHz network and a 2.4 GHz one.  I use the 2.4  because it goes through walls better than the 5Ghz one and gives me the full 600Mbps down/up that I pay for anyway.    All my devices including all the Sonos ones are connected to the 2.4 one.  So just now I turned off the 5GHz one . Result:  the offending Sonos message  about the wifi range extenders no longer appears.  So it looks like Sonos thought the faster network was a repeater and was warning me not to connect my devices to it even though none were and all was working fine?    I am going to update the  Sonos tech assistance guy who attended me  to se what he says.

One possibility is that the router does not allow 2.4GHz clients to talk with 5GHz clients. There may be a router setting to control this. The other option would be different SSID’s for 2.4 and 5GHZ, but don’t give SONOS the 5GHz SSID.

Maybe it's just that the two hidden 'networks' were both 5GHz so you have now  'accidentally' turned them off along with the  visible 5GHz network?

Or possibly set the “guest” network to have the same name as your normal network? I could easily see me doing that by mistake.

Thanks all.  
 

The 2.4 and 5 Ghz networks already had different names out of the box. I never changed any setting on the router till today when i turned off the 5Ghz one

the two other hidden networks sonos apparently  sees (according to the sonos tech guy who sees them in the diagnostic) are invisible to me. Even with wifi scanning software.  Only sonos seems to see them. they apparently have their one names too

i have no idea if they are 2.4 or 5ghz

anyway, none of this matters since the problem vanished as soon as i turned off the 5 Ghz network.I do not know if the phantom  networks are still there or not

Speaking to sonos tech, they also think the app was confusing the 5Ghz network with an imaginary range extender.  They are looking at it as being a bug in the app that they need to fix.

For me, the issue is resolved since i do not get the message anymore.

and the system always worked perfectly other than the little error message … and still works perfectly now that the message is gone. 
 

so i’m happy!  

thanks again!!