To fix HomeKit connection issues, please follow these steps:
Make sure that your iPhone and your Apple Home Hub (iPad, HomePod, etc.) are connected to a 2.4 GHz Wi-Fi network. All your iOS devices must be on the same network to be able to find each other.
Close the Apple Home app by swiping up.
Wait for at least an hour to give HomeKit time to update.
Set up the Smart AC Control V3+ with HomeKit again.
Please note: the Smart AC Control V2 and V1 are not compatible with Apple HomeKit.