Rachio 3 Not Responding in Homekit (Again)

@gizbug, earlier you wrote:

This suggest to me the HomeKit controller isn’t “seeing” the Rachio 3. So, basics:

. To what is the Rachio 3 connected? (Yes, WiFi, of course. 2.4GHz or 5GHz?)
. To what is the HomeKit controller connected? (Wired or wireless? If the latter: 2.4GHz or 5GHz?)
. Are the R3 and HK devices connected to the same WiFi SSID (if both wireless)?
. There is a facility on some WiFi routers and access points called “client isolation” (or something like it). That prevents wireless clients from “seeing” one another. Could that be what’s happening?