Dear Mr. Blasta,
I wouldn’t relax just yet - my Rachio3 now works about half the time (which is a huge improvement over this time last year when it could not be introduced to HomeKit for love nor money.)
But for the other half of the time it’s angry red icon central.
Nothing I do on my iPhone iPad or Mac makes any difference. Unplugging the Rachio and plugging it in again mostly gets it back into the HomeKit setup. Perhaps I should use a Smart plug for the Rachio, so if it isn’t responding I can turn its power off and on again using something reliable.
On just have the smart plug on a timed automation to turn off and on again at midnight and noon…