This is a very important point, and one that I explored with a fairly senior and helpful Apple tech... Though we didn’t arrive at a definite solution. Long story below, but with hope it will be helpful so someone.
My problem started in early February when I added a third HomePod mini, then upgraded it (and all my other devices, including a first gen Homepod and two Apple TVs) to the latest architecture, 16.3 for most of them. My home has about 30 connected devices, mainly Philips Hue lights but also some iDevices outlets.
After I made the addition and upgrades, every connected light/plug started to show “No response.” I could control these devices via their native apps (like the Hue app) but not via my phone, desktop, Siri, etc. The HomePods worked fine for standard stuff like playing music, getting weather reports, etc.
I tried everything obvious, including removing the Philips bridge from my Home app and then painstakingly adding everything back. Too forever... And it made no difference.
After several calls with Apple, I noticed that in the list of hubs the brand new Mini was listed as “Connected” while the others were listed as on “Standby.”
Once I unplugged the new Mini, it reverted to treating my main Apple TV 4K as “Connected”—and all the lights and plugs came back. I could control them all again as I had before.
Here’s the key thing: Some time ago extended my wifi network to an outbuilding (my barn, via TP-Link repeaters). The signal to the outbuilding is only 15% of the hardwired fiber bandwidth in the house, but it’s good enough for my purposes, which include a projector setup. I can still stream 4K movies there with the weaker signal. The uplink is similar—lower than the high-bandwidth in the house, but good enough.
But for whatever reason, it seems that when the new Mini in the outbuilding gets chosen as the Connected hub, HomeKit then fails to “see” all the connected devices in the house... Even though it shows up as part of my network, and I can do stuff remotely from the house like check the temperature in the room with the new Mini.
The outbuilding has a router of its own. The Apple tech theorized that for whatever reason, HomeKit was deferring to that router in choosing the Connected hub... which I can’t quite figure, since for example my main home Apple TV is actually right next to my router and has a far stronger connection.
It does seem that you used to be able to force HomeKit to prefer or prioritize among your hubs, but that this functionality dropped out with some recent update, maybe 16.2 or as late as 16.3. It would seem that Apple should restore that functionality.
The tech said that the software now runs some kind of network analysis/algorithm to “pick” the connected hub. It might just be whichever one is currently most active, or have something to do with how it assesses your network health.
His suggestion—though he admitted that IT is no longer his speciality—was to explore ways for my sub-router in the outbuilding to deter HomeKit from picking that Mini as the main connected hub. One suggestion he had was shutting off NAT there, which I can probably figure out how to do, but I too am not an IT pro, just someone who has tinkered with ports etc. when absolutely necessary, a lot of trial-and-error.
Anyway, the short-term fix is for me to not have the Mini in my outbuilding. I also have an AppleTV 4K in there, but for whatever reason my HomeKit has not prioritized it as the Connected hub or that has not resulted in the same loss of device controls, at least not that I’ve noticed.
Sorry for the long post, but this issue has not gotten much attention, and this was the first post I found which mentioned it. Apple, restore that function in the next update, please!
