Is there a new SSID/password on your router?  If so, see this link:

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

No everything else has connected ok.  My phone app will not work at all despite resetting and reloading it.  I cannot access the my account etc. as it is all greyed out.

Usually when functions are greyed out, it is a sign that the app needs updating. 

I’ve done that as well.  When I go onto the app there is now nothing whatsoever.

I am pretty sure that is your controller being unable to reach the app running on your speakers. 

Have you wired one of your speakers to your router, at least temporarily, to see if your controller can then connect? 

What is your router? Is it a mesh network device? How is your system normally connected?  Is there a VPN or work profile installed that may have changed its definitions in the background?

Have you tried to call Sonos Support directly to discuss it?

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 network and Sonos system. They also have access to hard data on your system, that those of us in this community don’t  

Thank you ….I think I need to resort to Sonos Support

Thank you for the help.  I have sorted it ….it wasn’t connected to the profile that it was on previously. 

So my internet service provider(ICP) updated their routers and automatically is set to 5GHZ. Sonos can only work on 2.4GHZ which is why Sonos does not connect via WIFI. It will work if I connect through my router via Ethernet but I didn’t want my SONOS in the spot of my router. My work around was to purchase a WiFi extender compatible with 2.4GHZ. You can purchase them on Amazon for cheap. You will then connect the WIFI extender via Ethernet cable to the back of your SONOS. I also had to use a small extension cord to fit the Ethernet cord to the back of the WiFi extender since it was on the bottom. I would recommend getting one with the Ethernet port on the side of the extender.  After that you can go follow the prompts on the app to connect. 
 

good luck all!

Sonos devices can often work on 5 GHz. You should check this FAQ. 

In short, it depends on your Sonos. 

SonosNet is a good option, especially for older Sonos devices, but the latest Sonos devices do not connect to SonosNet, only to a WiFi signal. 

I’d have a serious problem with an ISP limiting my choices like this…… Many devices can only do 2,4Ghz.

How did you fix this as I have the same issue?