Image cannot display on Android when Binding Image Source with an Url string (XAML)

This custom listview worked fine on Windows Phone but didn't on Android, there is a problem with binding Url source of Image. Any ideas?

`<?xml version="1.0" encoding="utf-8" ?>




<ListView.ItemTemplate>


<ViewCell.View>

            <Image x:Name="imgCell"
                   Source="{Binding ImageURL}"
                   WidthRequest="400"
                   HeightRequest="650"
                   HorizontalOptions="Center"
                   VerticalOptions="Center"
                 />

            <Label Text="{Binding Name}"
                   HorizontalOptions="Center"
                   VerticalOptions="Center"
                 />

            <Label Text="{Binding Rank}"
                   HorizontalOptions="Center"
                   VerticalOptions="Center"
                 />

            <Label Text="{Binding Cost}"
                   HorizontalOptions="Center"
                   VerticalOptions="Center"
                 />

          </StackLayout>
        </ViewCell.View>
      </ViewCell>
    </DataTemplate>
  </ListView.ItemTemplate>
</ListView>

`

Thanks.