Are you using an iOS or Android device? I use iOS and not seeing the path: Setting > Wifi. In iOS in the S2 controller the path is: Settings > System > Network > Manage Networks > Update Networks

You could do it the other way around - change the wifi password and SSID on your router to the credentials on your old router.

Hi! I had the same problem today. The Sonos app could not find my products on my new wifi and it was grayed out in the app. Over an hour later, after multiple attempts, I decided to try something new. I deleted the Sonos app from my iPhone and reinstalled it using my Sonos email and password. As soon as I did that, I reset my SL One and Beam to factory settings (hold the infinity button down in the back until it goes from orange and white flashing to green) and then you can add them back into the app - the app had no problem finding my products at that point and they were added to my new wifi. (Do make sure your Sonos products are on the Sonos site in your account when you log in before doing all this). It worked like a snap!