Blank title of NavigationPage

I am getting a blank title on the navigation bar.

I used tabbedpage with Navigation page,

Here is what my code looks like

App.cs

    public static Page GetMainPage ()
            {   
                return new NavigationPage(new CommonTabbedPage());
            }

CommonTabbedPage

public class CommonTabbedPage : TabbedPage 
        {
            public CommonTabbedPage ()
            {
                this.Children.Add (new PageType1 ());
                this.Children.Add (new pageType2 () { Title = "type 2", Icon = "type2.png"});
            }
        }

PageType1

 public class PageType1 : ContentPage
    {

        public PageType1 ()
        {
            Title = "type 1";
            Icon = "type1.png";
            ......
    }
}

PageType2

public class pageType2 : ContentPage
    {
        public pageType2 ()
        {
            .......
        }
    }

Any pointers shall help .... many thanks in abvance