Common Causes of Sync Errors

• Data validation conflicts: Duplicate attributes or invalid values, such as two users with the same User Principal Name, can trigger errors (AttributeValueMustBeUnique).

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• Hard match issues: Occur when the OnPremisesImmutableId does not match the target Entra ID object, often requiring restoration of soft-deleted users or removal of privileged roles.

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• Soft match issues: Happen when an object exists in Entra ID but has a different immutableId than the sourceAnchor, preventing proper matching.

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• Service not running: The Microsoft Azure AD Sync (ADSync) service must be running; otherwise, synchronization cannot proceed.

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• 3 Sources

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Step-by-Step Troubleshooting

1. Verify Sync Service Status

• Open Services and ensure the Microsoft Azure AD Sync service is running and set to Automatic startup.

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• If the service fails to start, assign the “Log on as a service” right to the ADSync service account using Local Security Settings (Secpol.msc).

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• 1 Source

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2. Use Entra Connect Health Dashboard

• Navigate to Microsoft Entra admin center > Health & Monitoring > Microsoft Entra Connect.
• Check Last Synchronization and Synchronization Status. Warnings or errors indicate issues requiring investigation.
• Click the Synchronization Errors tile to view failing objects and error types.

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• 1 Source

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3. Analyze Synchronization Errors

• Open Synchronization Service Manager on the sync server.
• Check the Operations tab for errors during import, synchronization, or export.
• Examine the Connector Space for missing objects and the Metaverse for data-related issues.

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• 1 Source

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4. Resolve Hard and Soft Match Errors

• InvalidHardMatch: Restore the user from the Recycle Bin, remove privileged roles, verify OnPremisesImmutableId, complete the hard match, then reassign roles.

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• InvalidSoftMatch: Ensure the target object has no immutableId set, allowing soft match to succeed.

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• 1 Source

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5. Address Data Validation Conflicts

• Identify duplicate or conflicting attributes in Active Directory.
• Correct the values to ensure uniqueness before re-running synchronization.

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• 1 Source

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6. Use Troubleshooting Wizard

• For Entra Connect version 1.1.749.0 or higher, use the troubleshooting task in the wizard to diagnose object-specific sync issues.

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• 1 Source

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Best Practices

• Regularly monitor Entra Connect Health to detect issues early.
• Keep Microsoft Entra Connect updated to the latest version.
• Document any custom synchronization rules to simplify troubleshooting.
• Test changes in a staging environment before applying to production.
  By following these steps, administrators can systematically identify and resolve synchronization errors, ensuring reliable data flow between on-premises Active Directory and Microsoft Entra ID.