IOS ST BLE Apps not able to connect to F401RE+IDB05A1. It shows 'Connection Timedout'. May I know what might be the reason? It works with Android

[MAb H.1]

- The .bin sample is from https://os.mbed.com/teams/mbed-os-examples/code/mbed-os-example-ble-HeartRate/

- The (iPhone) IOS Software version is 13.5.1, while the iPAD IOS Software version is 13.3

-The timeout time capture around 10s from 'connect' click till 'timedout' notification pop-up

How can this be fixed?