What September's Microsoft updates broke, and how to fix each one
If you look after the computers at a small business, September probably brought a few odd support requests. Office says it is unlicensed. The VPN sits on "Connecting". A PDF somebody saved to SharePoint is not there.
These were not unrelated. Each one traces back to a Microsoft update released in the past few weeks. Here are the five worth knowing about, in rough order of how much damage they can do quietly, with the fix or workaround for each.
1. Backups that stopped without telling anyone
This is the one to check first, because nobody notices a backup that has stopped.
After the September security updates, File History (the built-in Windows feature that copies a user's documents to an external drive or network storage) could stop working on Windows 10 and Windows 11. The signs are a "Reconnect your drive" message when the drive is plugged in and fine, and a "Last Backup" time that no longer moves.
Fix: on Windows 11, the optional updates KB5124010 (versions 24H2 and 25H2) and KB5124006 (version 26H1) repair it. Everyone else gets the fix in the regular monthly update of 13 October.
Check: open Control Panel, then System and Security, then File History, and look at the date of the last backup on any machine that relies on it. If it stopped in mid-September, there is a gap to close once the fix is in.
2. Office 2016 and 2019 showing as unlicensed
An update called KB5002907 was meant for out-of-date Microsoft 365 apps. It also landed on older, bought-outright copies of Office 2016 and 2019. Affected machines showed Office as an "Unlicensed Product", with a warning that features would be switched off within days. In some reported cases Office was removed entirely.
Microsoft has paused the update and says it is investigating.
Fix: re-entering the original product key restores activation. The Register reports it can take several attempts and a restart. If Office has gone completely, it needs reinstalling.
The bigger point: find those product keys now, while nothing is on fire. And note that support for Office 2016 and 2019 ended on 14 October 2025. They no longer get security fixes. An update breaking them is an inconvenience. Running them for another year is the real risk, and this is a good moment to put a replacement in the budget.
3. Always On VPN stuck on "Connecting"
Always On VPN is the Windows feature that connects a laptop back to the office network automatically. After the September updates on Windows 11, connections can hang or keep retrying, sometimes with the error "The specified port is already in use".
It happens when the VPN is set to try one connection method and fall back to another if the first fails.
Workaround: change the VPN profile from automatic to a single method, either IKEv2 only or SSTP only, whichever your setup already uses. Microsoft is working on a permanent fix.
4. PDFs saved to SharePoint that vanish
In Word for Windows version 2609, choosing Save As, picking PDF, and selecting a SharePoint location does not save the file there. It goes into a hidden temporary folder on the PC under a random name, and Word shows no error.
Workaround: use Export instead of Save As, or save the PDF to the computer first and then upload it. Tell the people who produce quotes, contracts, and reports. They are the ones who will assume a document was filed when it was not.
5. A black screen after signing in to a virtual desktop
This one mainly affects Azure Virtual Desktop, Microsoft's hosted desktop service, when it is used with FSLogix profile software. After the August preview update and those that followed, users sign in and get a black screen.
Workaround for the user: press Ctrl+Shift+Esc to open Task Manager, choose Run new task, type explorer.exe, and click OK.
Fix for the administrator: Microsoft has published a Known Issue Rollback, a group policy that reverses the faulty change. It needs installing, configuring, and a restart.
Do not stop updating
It is tempting to read that list and switch updates off. That would swap five nuisances for a serious problem. The same monthly updates fix security flaws that attackers use within days.
Three habits make months like this one easier:
- Let the monthly security update install, and leave optional ones alone. "Preview" and "optional" updates are early versions. Install them only when one fixes something you actually have, as with File History above. Note that KB5002907 was labelled optional, and one IT provider reported it installing itself on customer machines anyway.
- Update one or two machines first. If you can hold the rest of the office back by even a few days, problems show up on a test machine and not on the finance director's laptop.
- Check backups after every update round. It takes a minute per machine, and it is how you catch the failure that makes no noise. We wrote more about that in what makes a backup a backup.
If an outside IT provider handles your updates, the question to put to them is direct. Were any of our machines affected by the September problems, and did our backups keep running throughout?
How Steelwise can help
Setting up updates so that they go to a test machine first, and backups so that somebody is told when they stop, is a short piece of infrastructure advisory work. Get in touch if you would like help with it.