Fix Microsoft 365 Sync Issues: Expert Q&A Guide

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The M365 sync establishes a synced dataset based on your M365 data and the filtering configuration of your sync.



Troubleshoot Office 365 Sync and Login Issues

The sync will fail if it can't find any users that comply with your filtering preferences or the system's requirements for user records. The system requires that users have a first name, last name and a valid email address that conforms with your domain lock if enabled. The sync does not delete users but rather sets them to inactive. The idea is to provide a recycle bin of users who you can delete when you no longer need them.

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If a password reset in Office 365 isn’t syncing, users usually get sign-in errors or find old credentials still hanging around on devices. We focus on restoring sync between Microsoft Entra ID (Azure AD), on-premises Active Directory, and user devices so everyone gets back in without headaches. If password sync is off or the server is in staging mode, passwords won’t update. We turn password sync back on by running the Entra Connect configuration wizard and picking Customize synchronization options. Check that your password change actually synced between your on-premises Active Directory and Microsoft Entra ID (formerly Azure AD). If it didn’t, a few targeted checks usually restore access—no need to keep resetting your password over and over.

What to do when Office 365 password reset doesn’t sync across devices



Troubleshoot Office 365 Sync and Login Issues

To resolve these issues you should run the steps in this article and check whether the groups in your sync's filtering preference contain users in Azure AD. The simplest way to resolve authentication issues is to rerun the authentication process by clicking the Sign in with Microsoft on the Microsoft 365 settings page. You run the Microsoft consent process using an eligible M365 account after which you will be taken Repair Outlook Profile Online to the sync's setup wizard. You can close the wizard at this point as you do not need to complete it for re-authentication to take effect.

Login & Sync Errors: Personal & Business Microsoft 365 Accounts on Same Device



Troubleshoot Office 365 Sync and Login Issues

Bad settings in Azure AD Connect cause lots of password sync failures. If password writeback isn’t enabled or the service account doesn’t have the right permissions, new passwords won’t update in Active Directory. That leaves people locked out with their new password on the cloud but not locally. We show users how to reset passwords using approved methods like the Microsoft 365 portal or self-service password reset (SSPR). If someone changes their password only in the cloud or just on a local system, things can get out of sync pretty quickly.

Reviewing Device Sign-In Settings



Troubleshoot Office 365 Sync and Login Issues

The Summary sheet on the spreadsheet attachment of your sync summary includes an Updated User Count and User Limit. These figures will give you an impression of how far over the limit the account is. Sync failure alerts do not always include a full summary or Fix Outlook Not Opening After Windows Update attachment, you can run a test sync to obtain this data.



You'll also receive a mail (to the alternate resolve Outlook not sending emails fast email and to your admin email) from Microsoft 365 that indicates your tenant has encountered directory synchronization errors. For details see Identify directory synchronization errors in Microsoft 365. We check that the Work or School Account in Windows Settings is active and linked to the right domain. If there’s a sync error, we disconnect and reconnect the account.



  • Even I've only been doing this with test users so far, so haven't actually broken any actual users yet, I still need to get this resolved quickly.
  • We also scan Event Viewer logs under Applications and Services Logs → Directory Synchronization for Event IDs like 650–657 (for sync activity).
  • Running the Azure AD Connect Health tool gives you alerts for sync errors and interruptions.
  • We also check the synchronization scheduler to confirm delta and full sync cycles finish successfully.
  • Sync failure alerts do not always include a full summary or attachment, you can run a test sync to obtain this data.
  • You can stop any accounts from being brought over by adding them to the sync deny list.
  • Users I create within the Office 365 portal are fine, so I assume it is something to do with Azure AD Connect.


First, we check that the password reset finished in Microsoft 365 or Microsoft Entra ID. The user should log in to the Office 365 web portal with the new password. If the old password still works, the reset probably hasn’t synced. To avoid this, double-check that password writeback is turned on and working. You can run a sync manually with PowerShell or the Azure AD Connect tool to make sure updates go through. Checking the sync logs helps confirm password changes are making it everywhere they should.
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