*EDIT*  I just got off the phone with support. 

Apparrently, you cannot use the sub with the Ethernet port connected.  You HAVE to use wireless.   Which is odd, because I've only ever read that you must have everything wireless or everything wired to avoid packet storms.

Here's what they had me do:

1. Factory reset the sub (again).

2. If you disabled Wi-Fi on the Amp (or soundbar) because you had it on Ethernet, that was wrong.  Re-enable Wi-Fi.

3. Force close the Sonos app

     3a. If the sub still shows up, but not registered, you'll have to uninstall and reinstall the app (I did that earlier today)

4. Reopen the Sonos app, and select a+ Add speaker or component], and add the sub on Wi-Fi.

5. Go to the room you have your amp/soundbar assigned to, and select a+ Connect sub].  This last step took about 90 seconds for me.

And it works (for now).  I'll have to see if the packet storm issue is going to be a problem in the customer's network.  If so, I'll just return the sub and run an rca to a real subwoofer.

Original post:

So, I have a customer who just purchased over five thousand dollars worth of equipment for a whole-house Sonos system.  I told them that the ridiculous price was justified because the setup would be easy and everything would "just work".

So anyways, I've been trying to connect this sub for about three hours now.  I have yet to receive any guidance from Sonos Support.  I've been on hold for the last 45 minutes.

I'm a master troubleshooter, and I'm very good at following procedures.  I operated nuclear power plants on subs for over a decade, and I now own an IT managed services business.  If anyone should be able to make this work, it's me.

Setup done from Galaxy S21 Ultra on Wi-Fi 

Sonos Amp (Ethernet, wifi disabled)

Sonos Sub (gen 3, Ethernet)

Network at the office: Ubiquiti UniFi Network.  10gb fiber connecting the three buildings, PoE switches throughout, and an enterprise-grade router/firewall (not UniFi), and 1gb Fiber right into the server rack.

this worked for me!!! After hours of failed attempts and browsing through sonos troubleshooting (which is useless and cannot keep up with how incredibly bad the new app is).

adding the sub to a room did not work at first though (from the sub’s panel), but worked when I went into the room and then chose products to add to that room (in my case the sub)

i think sonos fired the entire testing team and released a new app without sit and uat…