Both iOS and Android apps will sometimes stop responding to the “Monitor Ambient” or “Flash Metering” controls on the exposure screen. The issue is the app’s UI state gets out of sync with the meter’s current state. This is a known issue and we’re working on an update.
The best solution is to disconnect the meter and reconnect. The app will refresh it’s state from the meter, and it should all work again. Sometimes tapping the “Monitor Ambient” or “Flash Metering” controls helps, by forcing the app to refresh from the meter’s state.