Microsoft Online Services Directory Synchronization tool stops syncing objects and triggers a Directory Synchronization error

Problem

You notice that synchronization of objects from your local Active Directory Domain Services to Microsoft cloud services has stopped. (These services may include Office 365, Microsoft Azure, and Microsoft Intune.)

Additionally, Event ID 0, or Event ID 109 is logged in Event Viewer:

Event ID: 0 or Event ID: 109

Source: Directory Synchronization

Description: This version of the Microsoft Online Services Directory Sync tool is no longer supported. Uninstall this version, and then download and install the latest version from your Admin Portal page.

Cause

This issue occurs if you're using a deprecated version of the Microsoft Online Services Directory Synchronization tool. We no longer accept connections to Azure Active Directory (Azure AD) if you're using a deprecated version of the Microsoft Online Services Directory Synchronization tool.

Solution

Upgrade to Azure AD Connect. This tool must be installed on a 64-bit version of Windows Server. For more information about how to upgrade from DirSync, see Azure AD Connect: Upgrade from DirSync.

More information

For more information about hybrid identity with Azure Active Directory, see Prepare for directory synchronization.

For more information about the system and software requirements for Azure AD Connect, see Prerequisites for Azure AD Connect.

For more information about the attributes that are synchronized by Azure AD Connect, see Azure AD Connect sync: Attributes synchronized to Azure Active Directory.

Still need help? Go to Microsoft Community, or Azure Active Directory Forums.