OK, for starters, once you get it connected, even briefly, set up Fixed schedule(s), which will run indefinitely without an internet connection, so the grass will stay green while you resolve the problem. (If you can’t get it connected at all, use a second phone as a temporary mobile hotspot, connect to that and set up your schedules.)
Assuming that you have the controller in with the 2nd quadrant blinking (awaiting Wi-Fi) and it advances to 3rd quadrant blinking when you reset Wi-Fi in the app, then the problem is most likely unrelated to your phone. Possibly, a firmware update in the APs or Pace has caused trouble, or a subtle change in signal strength or interference is responsible.
Let’s confirm that it isn’t something in a corrupted state: Remove power from the Rachio and all your network gear. Plug in the Pace and wait for it to come ready, then power up the Google APs and wait for them to come ready. Finally, plug in the Rachio and report what lights code is reached.
I’m not sure I understand. The Pace has a different SSID from the Google and you don’t normally use that, but you connected the Rachio to the Pace SSID for testing and that also failed. Is that correct?
Let’s make sure that you have plenty of signal. When connected to Google Wi-Fi, report the RSSI (Received Signal Strength Indication), then do likewise when connected to the Pace. Rachio displays RSSI only in the iOS app, but you can also view it on a desktop or laptop. For example, in Chrome, open app.rach.io, log in, select your controller, press F12, refresh the page, click the search icon, type ‘rssi’ (without the quotes) into the search box, press enter, mouse over the second line of the first hit and you should see something like this:
which shows an RSSI of -57 dBm. If yours is weaker than -75, that could be a problem.
If you have adequate signal, we’ll try some other tests.