App update issues

The random website thing might be an Apple or phone issue, not a Sonos one.

Not sure what you have done to your working setup that you are having to re-add devices. Maybe destroyed your existing system and started a new one? Loaded the wrong app version, or something else odd.

Start with getting and opening the correct app based on your old setup, S1 or S2.

Then start over and simple, power all down, reboot your router and controller. Then pick one speaker to work with to get back to a working setup, power it up. See if the app finds it and is able to control it. If so then run the update process. Worse case you may need a temporary Ethernet connection to do this, if you do then update your wifi settings and confirm it works without the Ethernet link.

Then add more speakers,  only power up one at a time and add it before going to the next.

TestFlight (I use it for another app that I beta) is a test setup that Apple uses to keep beta software up to date. It isn’t nefarious, but I’m somewhat surprised you’re being sent to it, unless you’re in a beta for Sonos. If you are, you likely shouldn’t be posting this issue in the public forums, but instead in the designated beta forums. 

To add to what has already been said, if you are running a VPN, turn it off so that it does not interfere with the connection between your phone and speakers

Another thing you can try is to connect one of the Play 3/1s to your router with an ethernet cable and update your network settings while plugged in.

Unless there is a good reason not to, using the same SSID and password from your old router would have been the simplest way to get your speakers connected to the new router.