Plupload addon doesn't work - what's wrong ?

I tried to use plupload addon.
I included the addon, recreate the widgetset (I didn't see any error) and added to a layout.
     Plupload upload = new Plupload("Update",FontAwesome.UPLOAD);
     hl.addComponent(upload);
I see the button but when I click on it nothing happened.
I expected the brows window would open but it doesn't happen.
Did I miss something ?
Could someone help ?
Tks