I have a Xamarin app working on UWP and macOS, and now being adapted to iOS, that communicates with a BLE device. The device includes a custom service, and a custom characteristic within that service that is configured for notification. The communication mechanism is that the app changes the value of the characteristic by using the CBPeripheral.WriteValue method with the CBCharacteristicWriteType.WithoutResponse option, and the device responds by changing the value of the characteristic. This should cause the delegate method UpdatedCharacterteristicValue in the app to be invoked. In the app running on macOS that works; in the iOS app it does not. The code is virtually identical for the two platforms. (Note that the mechanism works in a normal Objective-C iOS app as well.) I must be missing something, perhaps in that identical code used between the two platforms. Ideas?