ADSync won't start

Question

ADSync won't start - I am updated to the latest version in server 2019 and running hybrid with local AD

Answer 1

Hello, I hope you are doing well,

Here is a troubleshooting step that i personally used to see what's going on;

https://techcommunity.microsoft.com/discussions/azure/microsoft-azure-adsync-doesnt-start/3057130

https://learn.microsoft.com/en-us/troubleshoot/entra/entra-id/user-prov-sync/resolve-model-database-corruption-sqllocaldb

1. Check Windows Services:
   • Open services.msc and ensure Microsoft Azure AD Sync service is set to Automatic and try starting it manually.
   • Look for errors like “timed out” or “dependency failed”.
2. Verify .NET Framework:
   • Ensure required .NET version (typically 4.7.2+) is installed and not corrupted.
3. Inspect Event Viewer:
   • Check Application and System logs under Event Viewer for detailed errors (source: ADSync, DirectorySynchronization, SQL).
4. Check for Locked Accounts:
   • The service account used by ADSync might be locked, expired, or password changed.
5. Update TLS Settings (Optional):
   • If recently patched, TLS 1.2 might be required. Verify registry settings under: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols

Is possible that you have corruption too on the DB

SQL LocalDB Health: https://learn.microsoft.com/en-us/troubleshoot/entra/entra-id/user-prov-sync/resolve-model-database-corruption-sqllocaldb

• Run:

    
    "%ProgramFiles%\Microsoft SQL Server\150\Tools\Binn\sqlcmd.exe" -S "(localdb)\.\ADSync"
  

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Answer 2

The error in even logs is Azure AD Sync failed to start due to logon failure