See this thread…

https://en.community.sonos.com/setting-up-sonos-228990/sonos-components-google-mesh-wifi-go-wifi-or-sonosnet-6822265#post16322421

What most Google Nest WiFi users appear to do, is turn their ISP provided router into “modem or bridge mode” then wire the main Nest hub to that, followed by an unmanaged switch (plugged into the other Google hub port) just for any wired connections (if needed) ...and then put a 'more recent/modern’ Sonos device (Boost or Sonos One etc.) into the switch. If not using the switch, then just plug the Sonos device direct into this first main nest hub.

Importantly, if the ISP router can’t easily be placed in modem mode then the WiFi on that router needs to be switched off and the network ports should not be used for any further (other) wired connections.

Once the remaining Nest pucks/hubs are placed around the home and connected,  it’s then good to establish what WiFi channels are in use on the 2.4ghz band by those devices. To do that, you can use a piece of free software downloaded to  a laptop called “WiFiInfoView”, or similar software, which scans the airwaves and can identify the channels in use nearby.

There is similar wireless scanner software available for Android devices, but not much out there for Apple mobile devices (sadly). 

Over a day, or two, scan  and make a note of each WiFi channel in use by the Nest devices and try to find the  “least-used” non-overlapping channel ... eg. channel 1, 6, or 11.

Now set your SonosNet channel to that least used WiFi channel... and from time to time, just rescan and check that the channels haven’t changed. Always use the least-used channel for SonosNet.

Two further final points that are really worth doing here too..

• Providing you do not have a Sonos Move speaker remove/reset the WiFi credentials in the Sonos App “SettingsSystem/Network/Wireless Setup”. These are not needed when running the devices on SonosNet.
• A final further useful thing I would choose to do in your particular case, is to add the Sonos products IP addresses, to your Google Nest networks' DHCP Reservation Table.

Hopefully if you can understand and follow these few network suggestions you should find that your connectivity will improve.

Hope that information assists. 

I haven't made any changes to my isp router. To clarify I am going to change ISP as here in Australia we just connect to the NBN.

In prep for that I bought a Google Nest. It is running via an ethernet from my current ISP router. I then created a wifi network on my Google Nest named ABC. When I switch ISP's I'lll plug the NBN box straight in to the nest so will be a direct connection to the nest. 

Every other device in the house is now switched on to wifi ABC, but not Sonos. There is no switch coming from my Google Nest 

So it sounds like you need to switch off the WiFi signal on your current ISP router and connect a single Sonos product to your primary Google Nest Hub and ensure your mobile controller is on the Google Nest ‘ABC’ WiFi signal too… your devices with then operate in SonosNet mode.

Thanks,so for clarity you are saying I now need to have a sonos product always plugged in to the Google Nest?

This is not possible, all my speakers are mounted and away fro the Google Nest. That’s why I got Sonos, so I could be cable free...

I’m just a Sonos user like yourself and ‘No’ of course you don’t have to go down that suggested route, you can opt to set your devices running on your mesh WiFi instead, but many users with Google Nest Wifi appear to prefer to run the system in SonosNet mode (with one device only wired to the primary Google hub) and those that don’t choose to wire a speaker, may opt to use the Sonos Boost instead, but whether you wish to follow any of the suggestions, or not, is entirely a matter for you.
 

I’m just suggesting a setup that you ‘may’ find perhaps works best with such a WiFi mesh system. Please feel free to choose the Sonos setup you prefer… this document describes both types of setup that you can use:

Choosing between a wireless (WiFi) and wired (SonosNet) Setup

Remarked,

If you do decide to run your products on the Google Nest mesh WiFi only, then to switch WiFi Network you should hopefully find this document-link below helpful too in the steps required to make the switch (assuming you were not using SonosNet previously with your ISP provided router).
 

Anyhow I hope this assists:

Replaced your router or changed WiFi settings?