Do you only have a native app? Or also some “normal” pages? Are they accessible in the cloud?
As far as i know ( and it's also in the docs https://docs.mendix.com/howto/mobile/getting-started-with-native-mobile ) the make it native app only works when you are in the same local network. So you can't run your cloud apps this way. See https://docs.mendix.com/howto/mobile/native-builder for more information about creating app packages.