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

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: ''
 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

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)

 The remote name could not be resolved: ''
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Jose Gabriel Ortega CastroEE Solution Guide/Topic Advisor and CEO Faru Bonon ITCommented:
Well the exception is clear:
The remote name could not be resolved: ''

2 options: 1. Office 365 was down (at least some client's reported this from chile today, in a within 2 hours from now).
or 2 . you have DNS problems. if you can discard 2, then the problem is 1.
Create a ticket on O365 portal and review the admin center messages for information

EX172746 - Exchange Online - Service Degradation
Title: Unable to access Exchange User Impact: Users were unable to access the Exchange Online service. Final status: We've confirmed that service functionality has been restored and any residual impact has been remediated. Scope of impact: Our data indicated that customers located in Chile were most impacted by this issue; however, some customers located in other regions may have experienced impact related to this event. For customers impacted by this issue, it's likely most users were affected. Start time: Wednesday, January 30, 2019, at 6:00 PM UTC End time: Wednesday, January 30, 2019, at 10:00 PM UTC Preliminary root cause: A fiber optic cable responsible for datacenter connectivity was severed, which resulted in service availability issues. Next steps: - We're reviewing our monitoring services to look for ways to reduce detection time and more quickly restore service. This is the final update for the event.

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