Wire that Sonos One directly to the router with an Ethernet cable, it should the show up in the controller. At that point, you can change the network information in the controller, it will be changed on the speaker, and you can then remove the Ethernet cable.

This is all assuming you didn’t factory reset the device, something you should never do unless instructed. 

I have this exact some problem with an Arc SL. I didn’t change routers I just changed the name of my 2.4 network. It will not reconnect to the new network and it just keep getting this error:

There was a problem connecting your Sonos Arc SL to “”.

And it gets the error immediately so it appears it’s not even trying or errors out right away. Other devices like my Nest have reconnected to the network just fine. 

Please help!

Changing the SSID is essentially the same as changing the router. You’d previously told Sonos to look for network ‘X’, which no longer exists. You need to connect up your speaker with an Ethernet cable so it can be found, then update the information in the Sonos controller to look for ‘Y’, then you can remove the Ethernet cable, and your speaker(s) will find the new network. 
 

Remember, the Nest has a display so that it can ‘find’ and choose a new network, Sonos doesn’t. 

Hi,

Thank you for your replies.

I'll have a go with the ethernet cable, although I'll have to buy one. I also have a google nest mini (no display), which has connected to my new WiFi fine, although it is a different device completley. I'm wondering if it has something to do with my new Kcom WiFi, which has merged the 2.4ghz and 5ghz channels. It is slightly annoying but I'm not confident splitting them. 

Hopefully the ethernet cable works.

Thank you.

I know this is old, but did it work?

Yes, hook it up to ethernet and it works great!
 

Took a few tries to get it set up but the ethernet cable works fine. Not able to connect over WiFi still but it just sits near my router which is fine :)

It’s often a case of wiring one Sonos device only to the router (temporarily) and waiting 5-10 minutes for the other wireless Sonos products to switchover to what is often called ‘wired mode’, or SonosNet. All products should appear in the original Sonos controller App when one device is wired, that’s as long as you do not factory reset any of your devices.

If for any reason a device does not show up after 10 minutes then try rebooting it.

Once you have the devices showing, it’s then a case of navigating to ‘Settings/System/Network/Manage Networks’ in the Sonos App where you can select and remove any old WiFi network credentials and also go onto select the option to ‘Update Networks’ and follow the onscreen instructions to add your new WiFi network (cAsE SenSiTivE) credentials (SSID/Password) to all your Sonos devices. Once that’s complete you should then be able to uncable the wired Sonos device and if all is successful, after a short wait all your devices will switchover to using the new WiFi network.

Hope that assists.

Yes, plug speaker into router-delete old network settings from it in app-unplug from router-add new network settings 

I will confirm this option worked for me well.
I changed the router and wasn't be able to connect my sonos one to the network until I:
1. Connected one of my sonos directly to the router via ethernet cable
2. Opened the app and in settings > system > network > manage networks    deleted the old network and add a new one.
3. Unplug the ethernet cable

p.s. Merged 2.4hz and 5hz network still works. no need to separate it just for Sonos.
Done

I will report that, sadly, this solution did NOT work for me except as a wired connection. Even after leaving it connected for a really long time, and getting a notice that the network connected perfectly to the SONOS One (while wired), after disconnecting the wire the wireless connection continued to fail with the same message above. 
BUT!!!  Interestingly, there seems to be some sort odd incompatibility between SONOS and the iOS SONOS app  that caused my problem!  The connectivity was established instantly when I used my Samsung/Google app to set up the speaker. No delays, no error messages. Works beautifully now!  Not the first set of connectivity issues I’ve solved this way, either. I’ve found that Apple apps do not always work as well as Google apps when setting up wireless devices. 

It is a very easy fix. Wish sonos listed it here.. It happens when the speaker needs an update and it has not been used for a while. It will help if you can connect the speaker to an ethernet cable instead of Wi-Fi before you begin. First thing, please make sure your speaker is blinking green. There are articles here which describes how to get your speaker to the blinking green led state. I have the IKEA version, all I have to do is press the play button, and then hold it before plugging the power cable in. This will put my device into blinking green LED state. Then you have to do is go to your IOS or Android app > settings cog wheel icon > click on Reset app.. not reset the speaker or device.. you just want the sonos iOS/android app to be reset.. this will reset the Sonos app. Next enable the mic for the Sonos app from your phone. Now close and relaunch the sonos app. It will act like you are setting it up for the first time. It will quickly find the speaker and the speaker will play a Chime. Your Sonos app will listen to the chime and connect. So enabling your mic settings is critical. After that you’ll get a notification that your speaker needs a new update. Once your new update is downloaded, you’re good to go. The problem occurred to me because I did not use the ikea bookshelf speaker for more than a year. Hope this is helpful to all

This seems to be the only solution that works

I have been on the phone twice with SONOS, for a total of two hours, reset app, used Ethernet cord multiple times, allowed mic, deleted/reinstalled SONOS app, used a different phone for the app. NOTHING WORKS! Any help, please! 

Same problem, I’ve tried everything, been waiting for a call back on my phone for 4 hours, also waiting 2hour on wife’s phone, gen one app works but gen 2 for new speakers doesn’t work, I have had so many problems with connectivity over ten years, when it works it’s great when it doesn’t it’s useless. Shop and sales are useless too.

Hey there,

I have exactly the same issues with the speaker. Spend the whole day today with trying to connect.-unsuccessfully. Actually, nothing changed on the speaker and while connecte via Ethernet cable it works perfectly. But without the cable it is not possible anymore. Years ago it was still so easy and without any sound keys etc. I am pretty sure that sonos did this by intention to sell new models and get rid of the clients that still keep their old models.

if they do not fix this problem the next 2 weeks, it was DEFINITELY my last device of sonos.

I’m having the same problem with the NETGEAR Nighthawk X4 R7500v2 and Sonos One Speakers!

I just bought an ethernet cable (so outdated) at Staples and tried that, no luck.

Yes, I did a factory reset, because I thought I needed to after changing my network name and settings.

If you did a factory reset of all your Sonos products, in one fell swoop, you also need to create a new Sonos Household aswell to hold the products - but it all depends how you went about resetting the products in the first instance and which ones you cabled to the LAN. My suggestion is to perhaps contact Sonos Support and let them go through the steps with you - there should not need to be a reason to factory reset your devices, even if you change your router. Anyhow, here is the link to contact Sonos customer support:

https://support.sonos.com/s/contact

I contacted Sonos Support and they had no solutions. They told me to contact my ISP, as if they are the problem. I bought a new TP-Link router to see if anything would change. Nothing has changed. The TP-Link Router will only see a Sonos One speaker if it is connected via ethernet and factory reset. Once it is added and I disconnect the ethernet from the speaker to use it wirelessly, it disappears from the Sonos app, along with my Sonos Wi-Fi system.

So, either I wait until Sonos updates their app to work with these old Sonos One speakers, or I take them to Salvation Army and buy speakers from another company.

New router today = disaster. Sonos one no longer appears anywhere, can’t be found/located in network or anywhere else, ‘no products found’ in Manage Networks to reset WiFi network details, WiFi won’t connect, only Ethernet cable works. All WiFi 2.5ghz/5.0ghz/WAP2 checked, channel set to11, 6 and smart, etc, etc. Nothing works and nothing at all in the Sonos website solves the problem. 

Perhaps see this link:

https://support.sonos.com/en-us/article/connect-sonos-to-a-new-router-or-wi-fi-network

Thanks, but you’re kidding me right? I started with that article 4 hours ago.

I wasn’t kidding actually, as I have had no issues adding a new WiFi network to my Sonos system - in fact I have numerous networks added to my Sonos System - if you’re choosing to wire a player just remove the old WiFi network and use “Update Networks” to add the new SSID/password.

Having the same problem with my Era 100s and 300s. We're working fine connecting through my TP Link router. Switched to Verizon and set up with the same network name and everything connected fine. Just switched back to Spectrum and the TP Link, still set up with the same network name, and now none of the speakers connect. Connecting via ethernet isn't an option since I don't have the Sonos ethernet dongle, and all of the speakers are too far from the router, which sits in a closet.

So is the only solution to factory reset all of the speakers and set up again from scratch? 

Ok, solved my own issue. For me, the issue was the iOS app. I had the updated app on my phone and it couldn't find the speakers. Tried on my IPad, with an older version of the app and it worked fine. And now that the speakers are connected the current app on the phone works fine.