Attempt to present * on * whose view is not in the window hierarchy

I'm trying to make a modal view controller in my app delegate (I created a function called showLoginView). But whenever I try to call it I get a warning in XCode:

Warning: Attempt to present <PSLoginViewController: 0x1fda2b40> on <PSViewController: 0x1fda0720> whose view is not in the window hierarchy!

Here's the method code:

- (void)showLoginView
{
    PSLoginViewController *loginViewController = [[UIStoryboard storyboardWithName:@"MainStoryboard" bundle:NULL] instantiateViewControllerWithIdentifier:@"PSLoginViewController"];
    [self.window.rootViewController presentViewController:loginViewController animated:NO completion:nil];
}

How can I add the view to the window hierarchy? Or maybe I'm doing something very wrong?