There are several threads on this topic, but I haven't seen one that describes how to troubleshoot this. Last night, my homekit integration was not responding and all my hubitat devices were offline. I logged into my hubitat and installed the current update and rebooted. The reboot always fixes the issue, I mentioned the update because i didn't want to leave anything out. After the hub rebooted, Homekit was able to see and control everything again. This morning when I woke up, all the hubitat devices were again offline. I still have the makerapi homekit integration running for a couple devices that weren't supported in the official homekit integration. I checked those and they still worked correctly from homekit. I don't see any logs for the homekit integration and I'm unsure where to begin troubleshooting the cause. This happens often enough that I am beginning to think that maybe I should just move everything over to the makerapi integration. I want to try to troubleshoot the integration before I begin the task of moving all those devices over. Thanks in advance.
There is no way to troubleshoot it other than trying random things until you find a solution 
I know @gopher.ny has been working to try and make it more reliable recently.
I already had Homebridge setup (via the user integration app) before the system HK came out so I just left everything in there since it works great and is reliable.
There is a way to get the logs from Homekit but it's complicated enough that I haven't bothered. I believe you need a Mac, as well.
I too am having unresponsive HomeKit since recently updating my firmware.
I never should have updated and usually don’t. If it’s not broke don’t fix it.. But I wanted to be up to date, ughh.
I went from 2.3.8.xxx to 2.3.9.116 and now HomeKit is busted. It’s usually unresponsive. This is a big problem for me as I rely heavily on iPhone/Siri to control my devices. To be clear, I am not using an AppleTV or other Apple home hub.
Use the diagnostic tool to roll back the platform version. I would be sure you go back to 2.3.8.140 though as there was a critical z-wave logging fix in that build. If you don't have that as an option you can run this endpoint to download it first
HUB.IP/hub/advanced/downloadPlatform/238
I’m not sure if this is the right section for tech support as Hubitat doesn’t seem to provide any, but since last night NONE of my Hubitat devices are working with HomeKit which is the only reason I own Hubitat. Worked great for almost 2 years. Tried firmware rollback, restarting integration, rebooting hub, I can get it to work for a few minutes but then back to No Response on HomeKit. Of note, I upgraded to ios18 yesterday. Not sure if coincidence.
Is iOS 18 out or is that a beta version? There could be something Apple changed making it break, or could be a bugged on Apples side.
Both iOS 18 and tvOS 18* are now out as general release (* - or whatever the OS name is for Apple TV as a Home controller - Apple makes this aspect rather confusing since I think they have a different OS flavor for HomePods? not sure...)
I updated both my phone and (single) Apple TV last night and my HomeKit integration came through unscathed -- everything is working fine thus far.
Not beta. Regular version iOS 18. Given how many people have had issues with Hubitat HomeKit past few months on this thread I doubt this is something wrong with Apple. Only thing that helps is rebooting hub but it works for maybe an hour then back to not working.
Not in response to IOS 18 update but
I had a temperature device I was using that would return negative values. That was causing the homekit connection to go unresponsive. As soon as I removed that device, no more issues with "no response" EVERY SINGLE DAY. lol. Running good again for two months now.
I have a C7 in the house and a C8 hub in the barn. Only the house was going unresponsive, which the temperature device was connected too.
I would suggest as a test to remove the temperature reporting devices and see if that solves your issues. It was hard to catch the negative value, but it was crashing it.
I think I have seen people saying if a device reports battery greater than 100% that will also knock the HK connection down. Its possible any values that HK considers to be widely out of range will make the connection drop for some reason. Maybe HE is not handling the error response correctly?
I agree, that's what it seemed like to me. I have searched and searched for default high/ low values for HK or a range. No available info. Just people asking if they can use a homepod in a garage for the winter. lol.
It probably varies by attribute and the info should be in the HomeKit developer documentation somewhere. Not sure if that is out in the public, you may need to have a developer account to access those docs. HE team should have access to it.
If someone wants to setup a few tests cases, you could make a virtual temp sensor and something that has battery % on it. Share to HK and then set the virtual device to out of normal range values to see if that knocks the HK integration down.
