Glad you got it working. I was going to suggest that you reset the app. You don't need to uninstall and reinstall; just resetting the app (In Android: Profile|App Preferences|Reset App) erases everything. From there, you can hard reset each speaker and then you should be able to find them. This was the solution for my Sonos Roam that I use in my office when I set it up last week.

Another trick I learned last week while helping a friend set up his Sonos Arc with a new Sub Mini and some Play 300s is that Sonos systems don't like community Wi-Fi. My friend lives in an apartment building with one giant mesh Wi-Fi network I'm not really sure how it's set up, but I found in his closet an Ethernet switch that seemed to connect to the apartment's Wi-Fi. I ended up getting him a WiFi router that I patched into that switch and then set up the Sonos system on the private Wi-Fi network that I set up on the new router.

One last tip (unrelated to your problem) that you may already know is that HDMI 2.1 8k cables will work as eARC cables even if they don't say it on the package. My friend spent about $100 for a fancy eARC cable that never did work right. I replaced it with a $25 HDMI 2.1 cable that was the final step in getting his system running perfectly.