For your reference, here are the precautions for keeping the connection between the Xiaomi Smart Band 10 and an iPhone:
1. The device's Bluetooth connection, message synchronization, data synchronization, etc. rely on the Mi Fitness APP to continue running in the background. Please do not remove the Mi Fitness APP from the background;
2. If there are many applications running in the background on an iPhone, the system will close the background. If the Mi Fitness APP is closed, reopen the Mi Fitness APP and tap [Connect] on the device page to restore;
3. Check whether the device or phone has turned on the [Battery saver], which will cause Bluetooth disconnection.