This is an old thread, but seems appropriate. A few weeks ago my Gen3 Controller went “No Response” on HomeKit. I’m on an iPhone8, iOS 12.3 with AppleTV Gen4 hub. All the latest software. Trying your suggested troubleshooting steps 1-3 didn’t solve the problem, so I removed the controller and started configuration from scratch. After I was all setup again, I reconnected the controller to HomeKit. My connection lasted less than 30 minutes before returning to “No Response.” Rachio is the only accessory I have that’s not staying connected in HomeKit. I had no HomeKit connection issues with Rachio until a couple weeks ago.