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Bugs Killed

Windows

Teams and the new Outlook will not open on my Surface after the August update

On Arm based Windows PCs such as Surface Pro 11 and Surface Laptop 7, Microsoft Teams and the new Outlook for Windows fail to launch or close on their own after the Windows security update released August 11, 2026. Classic Outlook, Word, and Excel keep working. Microsoft resolved the issue in the September 8, 2026 updates and published a workaround for PCs that are not there yet.

Affects

Versions

  • Windows 11, version 24H2
  • Windows 11, version 25H2
  • Windows 11, version 26H1

Builds and updates

  • KB5121003
  • OS Build 26100.9168
  • KB5121000
  • OS Build 28000.2704

Apps

  • Microsoft Teams
  • new Outlook for Windows

Hardware

  • Arm based PCs, such as Surface Pro 11 and Surface Laptop 7

What you see

  • Microsoft Teams does not start, or starts and closes again straight away
  • The new Outlook for Windows does not start, or closes unexpectedly
  • Classic Outlook, Word, Excel, and other applications open normally
  • The PC is one of the "new or freshly imaged PCs that have not yet installed any Microsoft Store updates"

Why it happens

Confirmed Windows security updates released on or after August 11, 2026 leave Microsoft Teams and the new Outlook for Windows unable to start: Microsoft says both "might fail to launch or might close unexpectedly on ARM-based devices". It confirmed the issue on its release health dashboard and did not publish a root cause. [1] [3] [4]

Suspected Microsoft's workaround points at the Auto Super Resolution Package, a Microsoft Store component, which suggests an out of date Store package on new or freshly imaged PCs is part of the chain. [3] [5]

When it shows up

The Arm PC is on an update released before September 8, 2026 and the September update is not installed yet

You are in this case if:

  • Settings > System > About shows an Arm based processor
  • Update history lists KB5121003, or KB5121000 on Windows 11, version 26H1, and nothing newer
  • Teams and the new Outlook fail while classic Outlook and Word still open

2 fixes below

The Arm PC can install the Windows update released September 8, 2026 or later

You are in this case if:

  • Settings > Windows Update offers an update released September 8, 2026 or later
  • The PC is not held on an older update by an IT policy

1 fix below

The steps that killed it

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Keeping it away

  • On a new or freshly imaged Arm PC, open the Microsoft Store and install pending app updates before you rely on Teams or the new Outlook.
  • Check the Windows release health page for your Windows version when an app stops launching right after a monthly update.

Sources

  1. Windows 11, version 24H2 known issues and notifications
    Microsoft Learn, 2026-09-12
  2. Windows 11, version 26H1 known issues and notifications
    Microsoft Learn, 2026-09-12
  3. Microsoft Teams, Outlook fail to launch on ARM-based Windows PCs
    BleepingComputer, 2026-09-03
  4. Windows 11's August update broke Teams and Outlook on Arm PCs
    PCWorld, 2026-09-04
  5. Microsoft update disarms Outlook and Teams on Arm PCs
    The Register, 2026-09-02

First seen 2026-09-01 · Vendor status fixed · Fixed in KB5124008 (Windows 11, version 24H2 and 25H2) and KB5124012 (Windows 11, version 26H1), released September 8, 2026 · Last verified 2026-09-14