Microsoft fixes Teams, Outlook launch failures on ARM Windows PCs

Microsoft has fixed a bug that prevented Teams and Outlook from launching after installing updates released since the August 2026 Patch Tuesday.

The company confirmed last week that this known issue affects users who haven't installed Microsoft Store updates on ARM-based Windows devices (such as the Surface Pro 11 and Surface Laptop 7) running Windows 11 24H2 or later.

"After installing Windows security updates released on or after August 11, 2026, (KB5121003), Microsoft Teams and the new Outlook for Windows might fail to launch or might close unexpectedly on ARM-based devices, such as Surface Pro 11 and Surface Laptop 7," Microsoft explained in a Windows release health update.

"Classic Outlook, Word, Excel, and other applications are not known to be affected. This issue is most likely to occur on new or freshly imaged PCs that have not yet installed any Microsoft Store updates."

Although Microsoft has yet to disclose the root cause, it advised affected customers to update the Auto Super Resolution Package, which enables Copilot+ PCs to use AI to make gameplay smoother, as a temporary workaround.

Fixed by Patch Tuesday cumulative updates

On Tuesday evening, after releasing the September 2026 Patch Tuesday cumulative updates, Microsoft said it has now fixed the bug in KB5124012 and asked users to update their devices.

"This issue was resolved by Windows updates released September 8, 2026 (KB5124012), and updates released after that date," it said. "We recommend you install the latest update for your device as it contains important improvements and issue resolutions, including this one."

This is the latest in a series of other known issues caused by Windows updates released in August. On August 24, Microsoft also confirmed that August 2026 .NET Framework updates are breaking printing and PDF exporting in apps that use the Windows Presentation Foundation (WPF) UI framework.

Days later, it began rolling out a fix for a bug caused by peripherals with built-in RGB lighting that triggered gaming issues and system crashes with EXCEPTION_ACCESS_VIOLATION" errors on Windows 11 systems.

Microsoft also asked customers to ignore alerts that Microsoft Defender Antivirus has been turned off after installing updates released last month.

This week, Microsoft also resolved known issues that wiped custom mouse settings and Windows desktop settings on some Windows 11 systems after installing the KB5120998 August 2026 preview update.