I’m a little confused with your statement. Have you Factory Reset anything at this point? I hope not. Refrain from Factory Reset without further consult because you will simply be wasting time.

Are any of your SONOS units wired to the network? 

Why would you want to reset the Sonos One?

Factory resetting does nothing that a simple reboot will not do, except erasing important diagnostic and account data.

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

Or even just do https://www.google.co.uk/search?q=new+wifi+on+my+sonos

Why oh why do people think that a factory reset is necessary for this? I haven’t reset my entire system ever, and that’s in nearly 16 years. 

It should be renamed to ‘destructive reset’ instead.

It should be noted that a factory reset does not change the firmware version installed on your speakers.  OPs Sonos One will not suddenly revert to S2 when you do a factory reset.

But absolutely agree, factory reset is not the correct method for switching to a new WiFi network.

Thanks for all your comments. As mentioned, I would never do a factory reset unless all did not work and I have not done that yet.  I have 2 Sonos systems in 2 different locations. Both have 8 Sonos speakers. When I switched wifi providers in one location there were no issues. It was in a single home. The 2nd location- the one I am questioning- is in a condominium and the building has a master 5G Home internet fibre optic system router/modem(for lack of a better word)  and each apartment has a ‘gizmo’ that has its own password and picks up the signal from the master. I was told that I could plug the ethernet cable into the ‘gizmo’ but it did not work. I will try again when I arrive there in Oct .. No need to respond as until I know the proper terminology it is difficult to help. I will contact the wifi provider for that. Thanks for your help.