Question regarding Azure Authentication & Viewcontrollers

I've run into a problem with my application using a portable class library and xamarin.forms.
In my application you log in and authenticate using Azure active directory, it works when i call the authenticationmethod from my CustomViewController.
But when the user logs out and wants to re-login using a button (That is handled in a custom ContentPage), it doesn't work. i get an error that looks something like "can't present view AuthenticationAgentUINavigationController on UINavigationController whose view is not in the window hierarchy".
Any ideas on how to fix this? The problem is basically that i'm trying to present the authentication view from a class in my portable library.