Hey team! This is the latest update I have. This is by no means an official solution, but something our CS and Eng teams are investigating.
It seems that if a HomeKit user doesn’t have Apple TV, HomePod, or a configured iPad on the same network as the Rachio controller at all times, then the controller will go offline in the HomeKit app. This means that if a HomeKit user is using an iPhone and it switches to cellular, the controller will go offline in the HomeKit app. If they are using a HomePod, Apple TV, etc, they have to take the steps to ensure that the Apple device is connected to the exact same band as the Rachio 3 (which means they’ll need to configure their APs at appropriate distance from Rachio 3 and HomeKit device.) It seems that both the HomeKit hub and the Rachio controller need to be on the 2.4 GHz or 5.8 GHz network. The team found that if the Rachio controller is connected to the 2.4 and the HomeKit hub is connected to the 5.8, the controller will lose connection to HomeKit.
Does this apply to any of you? Again, this is just speculation at this point, but I’m working hard to keep everyone as updated as I possibly can!