Xamarin.forms Image doesnt display when binded to URL from ViewModel

Hello!

I have a MVVM project in wich I want to display items on a ListView. every Item has an Image and a description. I thing this is a basic use case. The images are on Internet. My problem is when I hardcode the image's hyperlink directly on the XAML like this, it works well :
<ContentPage.Content>


<ListView.ItemTemplate>









</ListView.ItemTemplate>


</ContentPage.Content>

But when I bind the Image to the hyperlinks from the ViewModel like this... :

...the images are not dislayed. The other binded data e.g: the Name, are well displayed with right values but not the images. Is it something I'm doing wrong?
FYI on the ViewModel, I simply hardcode the same hyperlink that was previous in the XAML. I tried a lot of thing resized, thy with image on the local machine etc. but got the same result. My page inherit from a BasePage that set the ViewModel as BindingContext and it works for the Name text. I verified the ItemsList collection at the runtime : the URLs and the names are there for every Items, but the Names are displayed, not the images.

Please help!