I'm using the native Homekit with two hubs. Both are working and have been solid. Today I moved some devices from one hub to the second one for load balancing reasons (longer story). I removed them from Homekit on the first hub without any problems. When I added them to the second hub they don't show up. I restarted Homekit a few times and still nothing. I then tried adding a few other devices and they don't show up either. So the integration appears to ignore all new devices now. I removed one and that worked -- went from 28 to 27 in the master list. I tried to re-add the one I removed and that didn't work either. The devices there work fine but can't add new ones. Anyone else seen this? I tried the restart option and that didn't help. I don't know how much disruption the 2nd and 3rd options are. The nuclear 4th option sounds ... well nuclear.
Solved my own problem -- had to upgrade HomeKit to the new architecture. All good now.
Thanks for posting. This is happening to me now with a pretty vanilla setup. No matter what I do, HomeKit isn’t showing any newly added devices that have been added via the HomeKit Integration app. I’ve been avoiding the new architecture (mainly because I like to know the technical details before a major upgrade, but they are very difficult to find) but it’s inevitable I suppose. I’ll upgrade and report back.
Update: after upgrading to the new architecture and rebooting the Hubitat, it now works. I see my new devices as soon as I enable them. I have no idea what’s different 
Update 2: This morning Apple Home showed all my Z-Wave devices as No Response. This hasn’t happened to me before. Regretting the “new architecture” upgrade already.
I wouldn't regret the new architecture; it seems to work fine with Hubitat. Something else must be going wrong. Sometimes Hubitat needs to reset Homekit periodically, so try turning on the option to restart Homekit once every hour. I have mine turned on and it seems to make it more stable.
Edit: resetting the integration seems to work. I'll try the hourly restart. Still, it was rock solid for a year before the upgrade to the new architecture...
When I awoke this morning, everything from Hubitat was "No Response" and none of the overnight HomeKit automations ran. Even with the hourly restart. I tried disabling and re-enabling the integration, no luck. The only thing that worked is rebooting the Hubitat.
My next step: I'm going to reduce the number of items exposed to HomeKit to a handful and see if that makes things more stable. If so, I will add new items one at a time.
Just want to close the loop on this one. As a recap, for a couple days after upgrading to the new architecture, all my devices would go “no response” in HomeKit after a few hours. I would, for example, wake up and find that my overnight HomeKit automations involving bridged lighting didn’t happen.
What I ended up doing was updating and rebooting all applicable gear, such as my WiFi, AppleTV, HomePods, etc. This worked for me back when ios17 was rolling out which was the last time I saw the dreaded “no response” from the bridged items. And this worked for me again. It’s been a few days since doing that and it’s back to being stable.
I will make sure in the future to do this full system reset anytime the HomeKit environment gets an update, seems to be the trick to ensuring a smooth transition.
That's a plan. I too a day or few ago was affected, but was confused because I was moving hubs and such to a new location (thought my 3 switches might have been poorly arranged). Essentially rebooted the entire home, all good.
