Error initWithContentsOfFile

Hi,
I'm trying to create in my Xamarin solution a project for macOS. I followed all steps from this document. When the application starts I receive and error:

    public override void DidFinishLaunching(NSNotification notification)
    {
        Forms.Init();
        LoadApplication(new App());
        base.DidFinishLaunching(notification);
    }

on the base. and the content is initWithContentsOfFile for

AppKit.NSImage..ctor(string fileName) in /Library/Frameworks/Xamarin.Mac.framework/Versions/5.2.1.13/src/Xamarin.Mac/AppKit/NSImage.g.cs:360

Do you know who I can resolve it? Thank you