I am in the same boat. And before anyone else replies and tells me to restart my Apple TV or my router, I am an IT Director with 30+ years of software and networking engineering experience. I have already gone through multiple rounds of extensive diagnostics to try to solve the issue. There is a serious issue between HomeKit and Hue. Also, all of my other HomeKit devices work, only Hue, and only since 26.4. I have over 80 hue lights, and am not going to go through the process of re-adding them one by one to HomeKit after deleting the link between the two. Unless there is a quick fix, I'm going to setup HomeBridge on a Raspberry Pi and access Hue via HomeKit that way.