Microsoft update disarms Outlook and Teams on Arm PCs

Not keen on the new Outlook? You're not alone. Microsoft's August security update has stopped it and Teams from launching reliably on some Arm-based devices, including Surface hardware. Microsoft acknowledged the problem on September 1 and added it to the Windows release health dashboard. "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