integration sharepoint 2013 with CRM 2011 The user authentication failed!

Question

voici le code merci de m'aider a résoudre ce problème :

                                

 var organizationUri = new Uri("https://*********/Organization.svc");
            Uri homeRealmUri = null;
            var credentials = new ClientCredentials();
            credentials.Windows.ClientCredential = new NetworkCredential("***", "***", "***");
            var orgProxy = new OrganizationServiceProxy(organizationUri, homeRealmUri, credentials, null);
            IOrganizationService _service = orgProxy;            

            List<Entities> EntityList = new List<Entities>();

            using (orgProxy)
            {


                RetrieveAllEntitiesRequest request = new RetrieveAllEntitiesRequest()
                {
                    EntityFilters = EntityFilters.Entity,
                    RetrieveAsIfPublished = true
                };

                // Retrieve the MetaData.
                RetrieveAllEntitiesResponse response = (RetrieveAllEntitiesResponse)_service.Execute(request);------>( The user authentication failed)

any help please :((((