NotificationServices' UnregisterForRemoteNotifications not persisting between game sessions?

I've put a button in my game to toggle notifications on and off. The button gets its toggle state from NotificationServices.enabledRemoteNotificationTypes, and to clear remote notifications it uses NotificationServices.UnregisterForRemoteNotifications().

When I run the app from xcode, the toggle button works correctly. Hitting it calls unregister, and the subsequent call to enabledTypes returns None. If I stop the app and re-run it, enabledTypes is no longer None.

Is this something to do with running from xcode? Is there something else I have to call to persist the data between sessions? The iOS documentation makes no mention of having to persist anything, and the unity class seems to map pretty well to that.