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I have a couple of HomeKit devices and, apparently like many people out there, I've had trouble getting remote access to work consistently. I thought I'd share my experience in case it is helpful to anyone out there.
Apple's HomeKit site states:
If you have an Apple TV (3rd generation or later), you can control your accessories with Siri commands when you're away from home. Just sign in to iCloud with the same Apple ID on your iOS device and Apple TV. https://support.apple.com/en-us/HT204893
When I first got my HomeKit-enabled ecobee3, I was excited to test out remote access via Siri (and my 3rd gen. Apple TV), asking what the temperatures at home were and changing things just to experiment. Remote Siri control worked for the most part, but I often had to make a request twice. I don't have much need, really, to check on temperatures and control things away from home, though, so I haven't used it much since the first couple of weeks.
At the time, I saw reports online of people having trouble getting remote access to work. I felt lucky to have a working setup!
Fast forward to last week, when I added by second HomeKit device: a Schlage Sense smart deadbolt. I chose Schlage since it matched the other hardware in my house and I could rekey it easily. I installed it and was very happy with the features: keypad, backup key, multiple codes with scheduling, iPhone app for editing settings, and HomeKit/Siri control. Unfortunately, I couldn't get remote access working, which, unlike the ecobee3, relies completely on HomeKit since it only has Bluetooth communication. I also found that my ecobee3's HomeKit remote access wasn't working, either.
I looked online for help and Apple's only troubleshooting step (for now) is:
If your remote access isn't working, sign out out of iCloud on your Apple TV, then sign back in. https://support.apple.com/en-us/HT204893
I tried that and left it overnight "for iCloud to sync" (Schlage's only additional tip), and it still didn't work. I tried removing both devices from HomeKit, resetting HomeKit via by phone, and restoring my Apple TV to factory settings and re-signing into my iCloud account. None of that worked, either.
Searching online more broadly, I found I was not the only one having trouble with remote access:
From the first link:
I signed in and out of iCloud on the Apple TV and on my iPhone many times during the testing period, but I could not get the Eve line of accessories to connect with my Apple TV. Elgato also walked me through a detailed (and frustrating) setup process that required un-pairing everything, re-pairing, and resetting my Apple TV, but it didn't work.
According to Elgato, there are problems with HomeKit on Apple's side regarding iCloud and certain Apple IDs, some of which simply don't work. Elgato's solution was to create a new Apple ID, but that's an unreasonable suggestion.
Our Apple IDs (and our iCloud accounts) are tied to a huge number of things in Apple's ecosystem and creating a new Apple ID and signing into a new iCloud account for a single accessory is an incredible hassle. It deletes Apple Pay cards, iCloud Photo Library photos, and Documents & Data stored in iCloud.
The (Ugly) Solution?
Like the author of that article, I was not prepared to change my Apple ID to make HomeKit remote access work - it's just tied to too much already. As an experiment, though, I figured it wouldn't be too much trouble to switch my HomeKit devices and Apple TV to use my wife's iCloud account. So I re-deleted all of my HomeKit settings and re-set up my ecobee3 and Sense deadbolt with her iPhone. I logged out of my iCloud account on the Apple TV and signed in with her account. I then added my iCloud account as a HomeKit "shared user" on her account.
And you know what? HomeKit remote access started working immediately and has been working for several days now. I can query my thermostat and lock via Siri when I am away from home, I can control my lock's settings via the Schlage Sense app when out of Bluetooth range (the app works a lot slower when using it remotely, by the way), and my other HomeKit apps (like Elgato Eve) no longer report "Unreachable" when I'm at work.
I have no idea why my wife's iCloud account works (at least for now) while mine has trouble. I may try to switch it back someday, but for now, I'm just glad it's working. I don't use many iCloud features on my Apple TV, so that's not a problem so far - I shared an iCloud photo album with my wife and got my custom screensaver back. On the HomeKit side, since my wife's account is the primary user now, I can only modify our HomeKit configuration (rooms, zones, scenes) via her iPhone, not mine. Since I am in charge of that stuff, that's a bit annoying, but I should only really have to change that when I add a new device or come up with a new "scene" to try, which is not often at all.
For now, I'm in a "satisfied, but slightly annoyed" stage as far as HomeKit goes. I do hope it gets a lot better as it matures (and that Apple comes up with some more concrete troubleshooting steps!). I knew more or less what I was getting into by trying this stuff out early in the game. I expect things will be more smooth as home automation and HomeKit become more mainstream.