Cross origin blocking despite subdomain exists in policy - ajax

Question

Hello I am trying to use cross origin from a subdomain (app.example.com) to www.example.com. When I try to execute the ajax I receive this:
XMLHttpRequest cannot load http://app.example.com/. The 'Access-Control-Allow-Origin' header has a value 'http://app.edentalbook.com' that is not equal to the supplied origin. Origin 'null' is therefore not allowed access.
I dont understand how I should use it..In my apache conf file I have those lines in order to enable cross origing policy:
Header always set Access-Control-Allow-Origin "http://app.example.com"
Header always set Access-Control-Max-Age "1000"
Header always set Access-Control-Allow-Headers "X-Requested-With, Content-Type, Origin, Authorization, Accept, Client-Security-Token, Accept-Encoding"
Header always set Access-Control-Allow-Credentials "true"
Header always set Access-Control-Allow-Methods "POST, GET, OPTIONS, DELETE, PUT"
My ajax call:
$.ajax({
method: "GET",
url:'http://www.example.com/index.php?logout',
crossDomain: true,
dataType: "json",
xhrFields: {
withCredentials: false
},
success: function(data){
loginPresta(email,password,companyName);
if(data == 'ok') {
}
},
error:function(data){
}
});