Can't connect to the band after clearing the app in the background on the iOS phone?

Open the Mi Fitness App to confirm whether the connection can be made normally:
If the connection cannot be made, click the connect button to see if the connection can be made normally;
If the connection cannot be made, confirm whether the device is connected in the Bluetooth of the mobile phone system. If the device is connected, ignore the device and confirm whether the connection is normal;
If the device is not connected, reset the device to factory settings and the App will rescan to connect to the device.