Siri Doesn't Recognize Your Device
Sometimes you will find that Siri does not recognize a device, for example Siri might say “that device is not located in that room” or something similar. Try these steps:
Temporarily change the name of one of the accessories.
Give it a half hour to propagate throughout iCloud and the rest of your system.
This action causes HomeKit to re-index your devices, which may fix your problem.
You can then go back and change the name back to your original name.