--- title: "Windows 11 September Update Can Stop File History Backups" url: "https://kesuk.net/windows-11-file-history-not-working.md" canonical: "https://kesuk.net/windows-11-file-history-not-working/" published: "2026-09-20" modified: "2026-09-20" author: "KES Team" tags: - "Backup & Recovery" - "Microsoft 365" - "News" - "Backup and Recovery" - "Microsoft" - "Windows 11" - "Windows 11 24H2" - "Windows 11 25H2" - "Windows updates" --- # Windows 11 September Update Can Stop File History Backups **Microsoft has confirmed that the September 2026 Windows 11 security update can stop File History creating or updating backups.** Affected PCs may wrongly ask users to reconnect a working backup drive, fail to update the last-backup time or show that previous file versions are unavailable. Microsoft is investigating, but has not yet published a fix. **What businesses need to know** - The confirmed problem follows Windows update KB5124008. - It affects Windows 11 versions 24H2 and 25H2 when File History is being used. - The backup drive may still be connected and healthy even when Windows reports otherwise. - There is currently no Microsoft fix or published workaround for the File History fault. ## What changed in the September Windows 11 update? Microsoft added the File History failure to the known issues for KB5124008 on 19 September 2026. The security update itself was released on 8 September for Windows 11 24H2 and 25H2, but the backup problem was confirmed later after customers began reporting failures. Microsoft says some File History users may be unable to create new backups or update an existing backup after installing the update. This is important because Windows can display misleading messages even when the external or network backup destination is connected correctly. Microsoft’s current position is: We are working on a resolution and will provide more information when it is available. No delivery date has been given. The update also contains important security fixes, so businesses should not uninstall it casually. The safer response is to check whether File History is actually completing and make sure important data is protected elsewhere while Microsoft works on a resolution. ## Which Windows PCs are affected? The confirmed File History problem applies to Windows 11 version 24H2 and 25H2 devices that have installed KB5124008 or a later update containing the same changes. It matters only where File History has been configured to back up files to an external drive or network location. PCs that do not use File History are not affected by this particular fault. Businesses using a separate managed endpoint-backup product should check that product independently rather than assuming this Microsoft issue has stopped it. You can check the Windows version under **Settings > System > About**. To inspect File History, open **Control Panel > System and Security > File History**. ## What will users notice if File History has stopped? The clearest sign is a File History warning that does not match the real condition of the backup drive. Do not dismiss it simply because the drive appears connected. | What users may see | What it could mean | | --- | --- | | “Reconnect your drive” | Windows may not be recognising File History correctly even though the drive is connected. | | The “Last Backup” time does not change | New or changed files may not have been copied. | | “No previous version available” | Windows may not be presenting earlier File History versions. | | FileHistory.exe or KERNELBASE.dll crash events | The File History process may be failing after the update. | ## Is File History the same as OneDrive or a managed business backup? No. File History, OneDrive synchronisation and a managed endpoint-backup service protect data in different ways. A File History fault does not automatically mean OneDrive or another backup platform has stopped, but it does remove one recovery route for businesses relying on it. - **File History** copies selected Windows libraries to an external drive or network location and retains earlier versions. - **OneDrive** synchronises supported folders with Microsoft’s cloud service. Synchronisation can reproduce accidental deletion or unwanted changes, so it is not a complete substitute for an independent backup. - **Managed endpoint backup** should provide monitored backup jobs, retention and recovery checks independently of File History. KES previously explained why [Microsoft 365 backup and recovery](https://kesuk.net/microsoft-365-backup-why-microsoft-is-talking-more-about-recovery/) need to be planned separately from everyday file access and synchronisation. ## What should businesses do now? Businesses using File History should verify the most recent successful backup rather than relying on the connected-drive icon. If the last-backup date has stopped moving since the September update, treat the device as temporarily unprotected by File History. 1. **Identify affected PCs.** Check for Windows 11 24H2 or 25H2 and confirm whether KB5124008 is installed. 2. **Check the actual backup date.** Open File History and compare the displayed last-backup time with when files last changed. 3. **Inspect a sample restore.** Confirm whether a recent document has an earlier version available. Do not overwrite the original during testing. 4. **Keep the backup drive connected.** Microsoft has not said the stored data is damaged, so avoid formatting or replacing a drive solely because of this warning. 5. **Provide temporary protection.** Copy critical new work to an approved alternative or confirm that a managed backup product is running. 6. **Watch for Microsoft’s fix.** Install the resolution when it becomes available through normal managed update procedures. Microsoft’s official [KB5124008 release notes](https://support.microsoft.com/en-au/servicing/os/windows-11/2026/09/kb5124008-windows-11-24h2-25h2-security-update) contain the current status and should be checked before making recovery or update decisions. Windows backup and support ## Not sure whether your backups are still running? KES can check affected Windows PCs, confirm whether recent files are protected and help put a monitored backup in place where File History is no longer sufficient. - Windows update and version checks - Backup-status and sample-restore checks - Managed endpoint-backup advice - Recovery planning for important business files Ask KES to check your backups → ### Already missing a file? Avoid repeatedly changing the drive or deleting backup folders. Tell us what happened and when the file was last available. See our data recovery service → ## What happens if the business does nothing? The immediate risk is not necessarily that existing backup files disappear. The more likely danger is that staff continue assuming new and changed files are being protected when File History is no longer updating them. If a laptop then fails, is stolen, becomes encrypted by ransomware or a user overwrites a document, the expected recent recovery point may not exist. The gap grows for every day that the failed job goes unnoticed. This is why a backup warning should be treated as an operational issue, not just an irritating Windows notification. A backup is only useful when its completion and restore process have been checked. ## Does the September update have any other known problems? Yes. Microsoft has also documented several separate issues affecting particular configurations. These include a domain trust failure on some Credential Guard-protected PCs, USB Audio Class 1.0 problems, File History failures and earlier Remote Desktop Services instability. The domain problem can prevent affected users signing in with valid credentials when Machine Identity Isolation enforcement is configured but the environment does not use Windows Server 2025 Domain Functional Level or later. Microsoft has provided a workaround for that specific problem and plans a future update. Other issues have already received partial or full out-of-band fixes. This does not mean every Windows 11 PC will experience a problem, but it reinforces the need for controlled update deployment and monitoring. KES’s earlier report covers the [security reasons businesses still need the September update](https://kesuk.net/microsoft-september-2026-security-update-zero-days/). ## Why does this matter to a UK SME? Small businesses often inherit backup arrangements that were configured once and then rarely checked. File History may be the only local recovery method on an older workstation, accounts PC or specialist machine, even if nobody currently describes it as part of the backup plan. A silent failure creates false confidence: the drive is present, Windows appears to know about it, but recent changes may not be recoverable. Businesses should record which system protects each important location and who checks failures. This is also a useful point to confirm that Windows versions remain supported. Windows 11 24H2 Home and Pro reach end of support on 13 October 2026; our guide explains [how to check the version and plan the move to 25H2](https://kesuk.net/windows-11-24h2-support-ends-october-2026/). ## Quick answers ### Has Microsoft fixed the File History problem? Not yet. Microsoft says it is working on a resolution for a future Windows update and will publish more information when available. ### Should businesses uninstall KB5124008? Not without technical assessment. KB5124008 contains important security fixes, so removing it could reintroduce vulnerabilities. Check the backup and provide alternative protection while waiting for Microsoft’s resolution. ### Does the warning mean the external drive has failed? Not necessarily. Microsoft says affected devices can show “Reconnect your drive” even when a compatible backup drive is connected and working. Check the drive separately before replacing or formatting it. ### Does this affect OneDrive? Microsoft’s confirmed issue concerns Windows File History. It does not state that OneDrive synchronisation is affected, although OneDrive should not be treated as a complete substitute for an independently monitored backup. ### Can existing File History backups still be restored? Microsoft has not said existing backup data is deleted. However, some users may see “No previous version available”, so verify recovery carefully and avoid altering the backup destination unnecessarily. ## The practical next step **If your business relies on Windows File History, check the last successful backup today.** Confirm whether a recent changed file has been captured, document any gap and make sure important work has another approved recovery route. Do not wait for a laptop failure to discover that the backup stopped after an update. If you would like KES to check a device or review the wider backup arrangement, [contact KES](https://kesuk.net/contact-us/). ## Sources - [Microsoft Support: KB5124008 for Windows 11 24H2 and 25H2](https://support.microsoft.com/en-au/servicing/os/windows-11/2026/09/kb5124008-windows-11-24h2-25h2-security-update) - [The Register: Microsoft patch gives domain-joined Windows PCs trust issues](https://assets.theregister.com/2026/09/17/202611/) *Checked 20 September 2026. Microsoft may update the known-issue status and resolution guidance, so affected businesses should confirm the latest release notes before changing update or recovery settings.*