Application cannot navigate to MainPage

I ran into a strange issue in my WP8.1 RT app - one of my beta testers reported seeing a black screen right after the splash screen. The application does not crash, hang up the phone or other - only black screen instead of MainPage. I have used some Trace methods in the code to track down the issue. The code looks like this:

// OnLaunched method that gets called when the App starts
protected async override void OnLaunched(LaunchActivatedEventArgs e)
{
    await Trace.WriteLineAsync(true, "Launched");
    Frame rootFrame = CreateRootFrame();
    await Trace.WriteLineAsync(true, "Before - better checkup");
    if (rootFrame.Content == null)
    {
        await Trace.WriteLineAsync(false, "Rootframe content was null, navigating");
        if (!rootFrame.Navigate(typeof(MainPage), e.Arguments))
            await Trace.WriteLineAsync(false, "Navigation false");
        else await Trace.WriteLineAsync(false, "Navigation was ok");
    }
    await Trace.WriteLineAsync(true, "After - better checkup");
    Window.Current.Activate();
} 

// Method creating the rootFrame:
private Frame CreateRootFrame()
{
    Trace.WriteLineAsync(true, "Create Root frame");
    Frame rootFrame = Window.Current.Content as Frame;
    if (rootFrame == null)
    {
        Trace.WriteLineAsync(true, "Root frame was null");
        rootFrame = new Frame();
        SuspensionManager.RegisterFrame(rootFrame, "AppFrame");
        rootFrame.NavigationFailed += OnNavigationFailed;
        Window.Current.Content = rootFrame;
        Trace.WriteLineAsync(false, "Window content {0}", Window.Current.Content.ToString());
    }
    return rootFrame;
}

      

        
        
        
      

    

The beta tester's log looks like this:

2014-10-06 13:02:56: Launched
2014-10-06 13:02:56: Create Root frame
2014-10-06 13:02:56: Root frame was null
Window content Windows.UI.Xaml.Controls.Frame
2014-10-06 13:02:57: Before - better checkup
Rootframe content was null, navigating
Navigation false
2014-10-06 13:02:57: After - better checkup
2014-10-06 13:03:01: App.cs suspending event

      

        
        
        
      

    

As you can see , the most important line Navigation false

, which means that

if (!rootFrame.Navigate(typeof(MainPage), e.Arguments))
     await Trace.WriteLineAsync(false, "Navigation false");

      

        
        
        
      

    

Navigation returns false - I can't navigate inside my frame, no crashes, no hangs - (event pauses), just can't get to MainPage. I disagree on what might be the source of the problem. Moreover, everything works on my phone, other devices are also being debugged and released.

Does anyone have an idea why I can't navigate to my MainPage?

Edit - Added navigation inconsistency:

void OnNavigationFailed(object sender, NavigationFailedEventArgs e)
{
    Trace.WriteLineAsync(true, "Failed to load page");
    throw new Exception("Failed to load Page " + e.SourcePageType.FullName);
}