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We have resources to help you identify potential issues and fix them. Whether Microsoft Office 365 won’t open, or you're facing persistent Microsoft 365 sign-in problems, our experts are here to help. Microsoft 365 is a robust platform, but when problems arise, fast resolution is key to productivity. From sync errors to sign-in challenges and collaboration setbacks, these common Office 365 troubleshooting techniques can restore service quickly. 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 to the sync's setup wizard.

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When they go back to the message and press send they get an error that the message has been deleted.I have multiple users experiencing sync errors with Outlook and office365.We have reset the router, checked internet speeds, signed in and out of M365 apps, reinstalled apps and checked for Windows updates.It seems to be some sort of error with the user not being able to connect and sync with M365 servers.Both of our authentication methods can fail if the Enterprise Applications entry for the sync in Azure AD is deleted or if it has had its permissions modified.If that doesn't resolve your missing users issue, please follow our guide to troubleshooting missing users below.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.

With apps syncing across devices and cloud services, sync issues are among the most frequently reported M365 problems. These can include missing files, ghost icons, or documents that do not update in real-time. The M365 sync establishes a synced dataset based on your M365 data and the filtering configuration of your sync. The sync will fail if it can't find any users that comply with Outlook data file cannot be accessed 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.

I got an error message that my company has exceeded the number of objects that can be synchronized

Our licensing engineers can help triage complex problems and ensure you're on the right support path. The error message in the Summary sheet of the Sync Summary spreadsheet attachment can also highlight the reason for this. Both of our authentication methods can fail if the Enterprise Applications entry for the sync in Azure AD is deleted or mailbox not updating on IMAP if it has had its permissions modified. You can stop any accounts from being brought over by adding them to the sync deny list. Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support.

What should I do if my sync failed due to authentication issues?

For details see Identify directory synchronization errors in Microsoft 365. Real-time collaboration is at the core of Microsoft 365; however, issues can arise due to permissions, software version conflicts, or connectivity problems. We go above and beyond the average software reseller because we built our business on trust. As active members in the IT community, we work to support our clients’ businesses and provide them with peace of mind. Find out what to do if you are having issues with syncing Fix Outlook and Office 365 Errors 2025 users or groups from Microsoft 365.

Tools & Methods To Use to Troubleshoot Office 365 Issues

The sync will fail if the total number of all users (active or inactive) on your account exceeds the user limit placed upon it if present. 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 attachment, you can run a test sync to obtain this data.