Binding property not found on ... some times

Hello ,

I'm new to xamarin, i've been codiging several versions, in all the versions i do the binding inside a stacklayout , like this ; BindingContext="{Binding NewDonner}" , some times the binding works , sometime don´t . I have visual studio 2015 community , the current version is Xamarin 4.6, the question is , xamarin updates can produce this behavior ?

ps.- may be this is not the right place to post the question, sorry if so .

Thank you