Question about MI Smart Kettle Pro - 451807

I am having massive problems connecting the MI Smart Kettle Pro to the app. - Tried 4 different mobiles - Bluetooth enabled on all and also resetted - Tried manual connect via device selection and also via QR scan; all unsuccessful. - Bluetooth on Kettle disabled, reenabled - Now and then I get to the point that the Kettle Pro is found, then I have to press boil again for 3 seconds to confirm, but nothing happens. Read all google results and tried. Does anyone have any tips? Many thanks