active directory, AAD sync, azure active directory

we are getting this error on our active directory


ES: Directory Synchronization::655 by Email Critical Events
Importance: High

EVENT #
 
2062568
MESSAGE
 
Failed credential provisioning ping. Error: Microsoft.IdentityModel.Clients.ActiveDirectory.AdalServiceException: user_realm_discovery_failed: User realm discovery failed ---> System.Net.WebException: The remote name could not be resolved: 'login.windows.net'
 at System.Net.HttpWebRequest.GetResponse()
 at Microsoft.IdentityModel.Clients.ActiveDirectory.HttpWebRequestWrapper.<GetResponseSyncOrAsync>d__2.MoveNext()
 --- End of stack trace from previous location where exception was thrown ---
 at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
 at Microsoft.IdentityModel.Clients.ActiveDirectory.UserRealmDiscoveryResponse.<CreateByDiscoveryAsync>d__0.MoveNext()
 --- End of inner exception stack trace ---
 at Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext.RunAsyncTask[T](Task`1 task)
 at Microsoft.Online.Coexistence.ProvisionHelper.GetADALToken(String userName, String userPassword, MSOInstance adalServiceResource)
 at Microsoft.Online.Coexistence.ProvisionHelper.GetSecurityToken(String userName, String userPassword, MSOInstance adalServiceResource)
 at Microsoft.Azure.ActiveDirectory.Connector.ProvisioningServiceAdapter.ExecuteWithRetry(String actionName, Action action)
 at Microsoft.Azure.ActiveDirectory.Connector.ProvisioningServiceAdapter.ProvisionCredentials(SyncCredentialsRequest request)
 at Microsoft.Azure.ActiveDirectory.Connector.PasswordChangeNotificationExtension.Ping(String forestInfo)
 ErrorCode: user_realm_discovery_failed
 StatusCode: 0
 
EVENT #
 
2062569

SOURCE
 
ADSync
 
EVENT ID
 
6900
 
MESSAGE
 
The server encountered an unexpected error while processing a password change notification:

 "user_realm_discovery_failed: User realm discovery failed

 at TargetExtensionManager.Ping(TargetExtensionManager* , ECMAInformation* ecmaInformation, Char* state, Int32* result)


 InnerException=>
 The remote name could not be resolved: 'login.windows.net'