Some routers generate two different Wi-Fi frequencies, one at 2.4 GHz and one at 5 GHz. tado° devices can only connect to 2.4 GHz WiFi networks.
To set up your Smart AC control correctly with HomeKit, please make sure that your iOS mobile device is connected to a 2.4 GHz Wi-Fi frequency. More information about network specifications can be found in your router’s manual.