I would first ensure that you’re using the latest Sonos App for your mobile device. You can either get that from the App Store, or check and download it from here…

https://support.sonos.com/en-us/downloads

Then see this link for what you need to do after that…

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

The first link above for the download says to check compatability by going to settings/ system. App won’t let me click “system”. The app store gives me the option to open, but not get. I presume this is because I have that app already? (Also, support in the app offers “downgrade to S1. )

At the 2nd link, for S2 it says to click on “lets fix it”. That leads to cannot find the system & tells me to upgrade network. Clicking on ugrade network leads to cannot find system.

For S2 it says click” learn more” than click “changed router or system”, That link does not appear anywhere. I am going in circles.

What would happen if I deleted the sonos app & re-downloaded it. I read it a previous conversation that sonos would lose data & it might be more difficult to reconstruct.

The App is just a remote - all the information/settings are held on the speakers, so you won’t lose anything by deleting or resetting the App - which controller device are you using? 

I don’t know where you read that, but it is 180 degrees from the truth.  The app itself contains almost no data.  All system, accounts, services, playlists, local library, favorites, etc. data is stored on the Sonos devices themselves.  There is zero risk in deleting the app and re-downloading it. 

Thanks. I just reset the app. Same problem. Cannot find the system. 

I am using an iPhone 13

Sounds like a router issue, try cabling one standalone Sonos product to the new router and see if that causes the system to appear in the App.. give it a few minutes to show.

Plugged in a cable. It said to push button on the back. Light on top of speaker went from solid white to blinking orange, but never connected. Waited several minutes, but nothing happened.

Appears to have been a bad cable. Tried a different one & could update. Thanks for your help.