Since the June 2026 Windows 11 update, Word, Excel, and other Office apps silently fail to open when launched from inside another program. Practice management suites, accounting packages, document tools, anything that opens Office through automation just stops working, usually with no error message at all.

Microsoft confirmed the bug in KB5094126, the June 9, 2026 cumulative update for Windows 11 24H2 and 25H2, and shipped the fix a month later.

Quick Fix

Install the July 14, 2026 cumulative update KB5101650 or anything newer. Settings, Windows Update, Check for updates, reboot. That's the whole fix.

Confirm the installed build afterward. You want build 26100.8770 or higher on 24H2, 26200.8770 or higher on 25H2:

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If Windows Update won't offer the July update, our update repair guide below covers unsticking it.

What Was Breaking

The June update broke OLE automation, the mechanism third-party software uses to launch and drive Office applications. Affected software Microsoft named includes CCH Engagement, Workpaper Manager, Dentrix, Softdent, and Zotero, and the same failure hit anything else that opens Word or Excel documents through automation. The Office apps themselves ran fine when launched directly, which made this maddening to diagnose: Office looked healthy, the line-of-business app looked broken, and the actual culprit was the Windows update underneath both.

Microsoft: KB5094126 release notes and known issues

If Updating Didn't Fix It

A machine on the July update or later that still can't launch Office from a third-party app has a different problem.

Repair Office. Settings, Apps, Installed apps, find Microsoft 365, Modify, then run Quick Repair first and Online Repair if that fails.

Re-register the automation server. Some line-of-business vendors shipped their own workarounds during the broken month that now need to be undone. Check the vendor's support notes before reinstalling anything.

Check the app's bitness. Automation between a 32-bit line-of-business app and 64-bit Office has its own long-standing quirks unrelated to this update. Your vendor will know which combination they support.

Fix: Microsoft 365 Apps Won't Open on Windows

Fix Windows Update Errors 0x80070002 and More

Fix Classic Outlook MSVCP140.dll Crashes

Line-of-business software breaking every Patch Tuesday? Contact Rain City Techworks.