I heard the following from Rachio:
This has been escalated to the engineering team in order to get the 6-digit code you might be missing to properly integrate the Tempest on the Rachio App.
Once I have an update for you, we will let you know but for now, since this will also require an app update release, I can’t provide a time frame on when will this be resolved.
Thank you for the time and patience, we really appreciate it!
I read this as Rachio having to patch its app to permit integration for those who already owned the Tempest weather station. Hopefully, I am correct and will advise as soon as I learn more.