What brand/model router are you using? Have you tried rebooting your router and unplugging  your One for about a minute?

Have you tried following the instructions here:

https://support.sonos.com/s/article/1061?language=en_US

Thanks John B.  I'll try it and let you.

AuthenticallyMe

GuitarSuperstar,

I’m using a TMobile SSID router. And yes I’ve rebooted. I keep getting this message “No Sonos fount on T-Mobile” And I am unable to access system while in settings to connect wirelesssly.

Thanks for your help. Anything else I can try.

AuthenticallyMe

Can you connect one of your Ones to the router with an ethernet cable to see if that makes a difference?

Might be helpful if you were to provide a link to the manual for this router, so we could look at specifics, in order to assist you. 
 

No ethernet cable but here's the link to the manual 

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.t-mobile.com/support/public-files/attachments/T-Mobile%2520High-Speed%2520Internet%2520Gateway%2520End%2520User%2520Guide.pdf&ved=2ahUKEwiUqIjFhZXvAhXqT98KHW31DVsQFjASegQICRAC&usg=AOvVaw1S_52Q6Zz_HuGDflfu-XgA

I don’t think this device has router functionality at all.  It’s referred to as an internet gateway only...more like a modem or hot spot.  It seems that it allows devices to connect to the internet, but doesn’t assign local IP address and allow devices on your network to connect to each other...requirements for Sonos to work.

Could be off on this, but nothing in the user manual makes me think otherwise. That doesn’t mean you can’t use this for internet access in your home, but I suspect you will need to turn off the wifi and connect an actual router with WiFi capabilities in order to create a typical home network that Sonos can use.

So that means I need to purchase an internet plan with someone else, right? Wow, first HULU, now my Sonos. So much for cutting the cord. 

Thanks everyone for all your help.

AuthenticallyMe

Not sure I agree with Danny on this. It appears to be a router that creates a WiFi signal, in addition to being a modem that connects to T-Mobile. It’s similar to the device AT&T gave me years ago. iI chose not to use that device except as a modem, and use a Netgear router connected to the modem, but this is a personal choice. 

As GuitarSuperstar suggests, are you able to, at least temporarily, connect the Sonos One to either of the two RJ45 ports on the back of this?

I’m mildly concerned, not having read the manual end to end (and thank you for that link!), that your Sonos devices may be connecting to the 2.4 GHz channel being broadcast, and your controller device is connected to the 5Ghz channel, and this router isn’t passing data between the channels. Wiring a speaker directly to the back might prove that case for us. 

That’s not what I said at all.  Nothing wrong with your internet plan, I’m just not sure that the device you were given by T-Mobile acts like a normal home router, allowing devices connected to it to communicate with each other as well as connect to the internet.  You can go get a router separately.  This is what I, and many others actually do...use a third party router setup (often mesh network) instead of or in addition to the device provided by whatever internet service provider you use.

As far a ‘cutting the cord’, I’ve only heard that in reference to dropping your cable or satellite TV service, in favor of using over-the-air antenna and/or streaming services.  Wasn’t aware that it implies getting internet from a wireless provider instead of wired service.

I’m not sure I agree with me either, hence I used uncertain language. I searched through the user manual looking for the words ‘DHCP’, ‘IP’ , anything that would talking about assigning internal IP addressed.  Not very reassuring.

Good news! I was able to reconnect my Sonos One speakers using an ethernet cable, although I had to connect each one separately. But now they both work and I was able to pair them for stereo sound.

Thanks so much to everyone who helped me. 

AuthenticallyMe 

@AuthenticallyMe I just received my trash can a few days ago and getting awesome speed up to 300Mbs. I too unable to connect my Sonos wirelessly to my network using my T-Mobile gateway. Did you take the trash can to each speaker and connect via Ethernet to allow it on your network?

Yes, that’s exactly what I did.

@AuthenticallyMe So I spoke with Sonos support today.  They asked if I had an Ethernet cable as a fail safe. But they had me go into the App> Setting> Network> here I remove my older network from even my new one. From here I was able to connect to the Nokia gateway.  Just happy to get it working.

Awesome!