Microsoft patches Teams and Outlook ARM launch bug

Microsoft has fixed a bug that stopped Microsoft Teams and the new Outlook for Windows from launching on ARM-based Windows devices, according to a report by Bleeping Computer published September 11, 2026. The fix arrived with the September 2026 Patch Tuesday cumulative update and affects devices such as Surface Pro 11 and Surface Laptop 7 that had not yet installed Microsoft Store updates while running Windows 11 24H2 or later.

ARM-based Windows PCs run on a different processor architecture than traditional laptops and desktops, which means some software components delivered through the Microsoft Store must be kept current for modern apps to work properly. The affected devices include Microsoft's own Surface Pro 11 and Surface Laptop 7, two thin and portable Windows 11 systems commonly used for everyday productivity.

The company confirmed the known issue last week and explained it in a Windows release health update. After installing Windows security updates released on or after August 11, 2026, which Microsoft identifies as 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. Classic Outlook, Word, Excel, and other applications are not known to be affected. Microsoft said the problem is most likely to occur on new or freshly imaged PCs that have not yet installed any Microsoft Store updates.

Microsoft has not yet disclosed the root cause. As a temporary workaround, it advised affected customers to update the Auto Super Resolution Package, a component that enables Copilot+ PCs to use AI to make gameplay smoother. On Tuesday evening, after releasing the September 2026 Patch Tuesday cumulative updates, Microsoft said the bug was resolved in KB5124012 and recommended that users update their devices. The release notes state that this issue was resolved by Windows updates released September 8, 2026 (KB5124012), and updates released after that date, and that the latest update contains important improvements and issue resolutions.

The Teams and Outlook launch failure is the latest in a series of known issues caused by Windows updates released in August. On August 24, Microsoft confirmed that August 2026 .NET Framework updates were breaking printing and PDF exporting in applications that use the Windows Presentation Foundation (WPF) user interface framework. Days later, the company 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 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.

For IT teams and website owners who run Windows-based office environments, the launch failure shows why patch releases need to be paired with careful update management. Teams and the new Outlook are central communication and productivity tools, and a device that cannot open them after a routine security update can interrupt daily work. The affected configuration is specific to ARM-based Windows hardware that has fresh or newly imaged installations and has not yet received Microsoft Store app updates, so staged rollouts and store updates before production use are practical safeguards.

Organizations that want to keep Windows fleets patched without introducing known issues can turn to AEU-I, a security-first IT and infrastructure consulting service, for help planning and testing update rollouts. The September fix is available now, and Microsoft encourages users to install the latest cumulative update to get the resolution along with other improvements.