With one or more Sonos devices connect to your router (or via a switch), you are in what Sonos calls ‘wired mode, or sonosnet.  You could say that your speaker connected to the router is effectively the gateway.  However, without a wired device, your system is in ‘wireless mode’, where every device connects to the router over 2.4 Ghz.  There isn’t any gateway with this setup, no phone or tablet is acting as a gateway.  Each phone or tablet  is just a controller in any setup.

I’m not a network expert, but I suspect that there was some other network issue that caused issues with your Note 8.  Could be an access point in your network that Sonos or the note 8 was connected to, or something of that nature.

Thanks for you input Danny. 

Doesn’t explain why it was working fine, then simply stopped. Only change being a security update on the S9+, not even on the Note 8.

I forced everything to be on 2.4Ghz to no avail. I read elsewhere how having the “wireless” ARC to be wired as a solution…

The kicker is how the Note 8 in the Sonos 2 app saw instantly all the ARCs once one was wired, and would just spin for minutes and fail before. Sometimes a full reset of *everything* would make the Note 8 work, for a few days, then would mysteriously fail again.

Almost as if I used my S9+ just once to access Sonos, it would “kick out” the Note 8 (both using my email & password and the same Wifi network).

At least there’s a solution, have one be wired. Buy an “extra” speaker to have one be wired, to not lose your existing spearkers and further the “sunken cost fallacy”.

This issue has me reconsidering my TV sound-bar upgrade to NOT be a  Sonos product, even though it supports the audio HDMI (eARC) pass-through.

Was the new router some sort of mesh device? I’m with Danny here, it sounds like the Android device was connected to a different subnet than the Sonos was. 

I understand that it may have felt that way, but it’s only coincidence that the S9+ appeared to have some sort of impact on your Note 8’s access to Sonos.  The Sonos app is just a controller.

Your situation does not necessarily apply to others.  There certainly are cases where people have network issues in a ‘wireless’ network, and a wired network is a solution, but I doubt many have the issues between S9+ and Note 8 that you were seeing.  Regardless, you don’t have to buy an extra speaker, as Sonos sells the Boost for this purpose, if you can’t conveniently connect one of your speakers.

If you don’t want the soudbar anymore, then sure, return it.  For the connectivity issues though, I would at least talk with support before concluding you have to use wired.  They have diagnostic tools that may be able to tell you exactly what’s going on.

The network is a simple home one, on 192.168.2.x, the router is the ISP one.

From my laptop I can ping all of them, and on the Note 8 it’s able to print through the network, access the internet, etc.

I haven’t bought a Sonos soundbar yet, I just have the pair I bought at Costco last year. They are PLAY:1 models.

IOW, all things being equal, when both are in wireless wifi mode, only my S9+ works flawlessly. The Note 8, when I get it working (full reset of everything) it “loses” the ability to use Sonos if I use the S9+.

However, I just tested this again, but keeping one speaker “wired” to the router. The Note 8 had picked a music station on Sonos, on the S9+ I took over and chose a local music station, this worked, then on the Note 8 went into Spotify and picked Sonos for a playlist, and it worked flawlessly.

Previously, this would “break” the setup. So having one speaker wired has made this 100% reliable.

I’m a lot happier now. Hopefully this discussion will help others.

Your thread title says Arc.  You mentioned owning 2 Arcs in your first post.   Your profile says you own an Arc.  So either you aren’t being truthful, don’t know what an Arc is, or were talking about someone else's home you were troubleshooting for?