Teams and Outlook Not Opening on Windows 11 ARM? What KB5121003 Broke – and How to Fix It (2026)

Surface Pro 11 owner, and Teams just stopped opening this week? Check the build number before you do anything else. As of September 1, 2026, Microsoft’s own release health dashboard lists this as a confirmed, mitigated issue tied to OS build 26100.9168 — not a random glitch on your machine.

Quick Jump

What’s Actually Broken in KB5121003?

KB5121003 shipped on August 11, 2026 as a routine security update for Windows 11 versions 24H2, 25H2, and 26H1. On ARM64 hardware, it does something it shouldn’t: the new Outlook for Windows and the new Teams client — both packaged as MSIX apps — either refuse to launch at all or open for a second and then close.

Classic Outlook is not affected. Word, Excel, and most other Store apps keep working fine. That narrow blast radius is actually the clue to what’s going on, which the next section gets into.

When I checked Microsoft’s own release health page directly, I found the issue was logged as “most likely to occur on new or freshly imaged PCs that have not yet installed any Microsoft Store updates” — so a brand-new Surface out of the box is more likely to hit this than a machine you’ve had running for months.

Fix Method 1: Update the Auto Super Resolution Package

This is the workaround Microsoft itself published, and it takes about two minutes.

Step 1: Open Microsoft Store on the affected PC

Search for “Store” in the Start menu and launch it. You don’t need Teams or Outlook open for this — in fact, they probably won’t open anyway.

Step 2: Check for and install pending updates

Select Library > Get updates (or Downloads > Check for updates on older Store builds). Let every pending update install, but specifically confirm the Auto Super Resolution Package updates to version 1.0.19.0 or later — that’s the exact version Microsoft names as the fix.

Step 3: Restart Teams and Outlook

Close both apps fully from Task Manager if they’re stuck in the background, then relaunch. Most reports on the Microsoft Q&A thread say the apps open normally on the first try after the package updates.

Honestly, that’s usually enough. If it isn’t, move to Method 2 below rather than repeating Step 2 — reinstalling the same package twice doesn’t change the outcome.

Fix Method 2: Roll Back the Update

If the Store won’t update the Auto Super Resolution Package, or Teams and Outlook still won’t launch afterward, rolling back KB5121003 restores function immediately — but it’s a temporary step, not a real fix.

Step 1: Open Windows Update settings

Go to Settings > Windows Update > Update history > Uninstall updates.

Step 2: Uninstall KB5121003

Find KB5121003 in the list and select Uninstall. Restart when prompted.

Step 3: Pause updates until the fix ships

Pause quality updates for 7 days from the same Windows Update screen so the same build doesn’t reinstall itself overnight and undo the rollback.

This part trips a lot of people up: DISM and SFC scans, and even a factory reset, do not prevent the bug from coming back once KB5121003 reapplies. Uninstalling the specific update is the only rollback path that has actually worked in reports so far.

Why Does This Only Hit ARM Devices Like the Surface Pro 11?

It comes down to how MSIX-packaged apps handle graphics driver dependencies on ARM64 silicon. Teams and the new Outlook both lean on the Auto Super Resolution component for display scaling on Snapdragon-based Surface hardware — x86/x64 PCs don’t route through that same component, which is why Intel and AMD machines haven’t reported the crash.

Surface Pro 11 and Surface Laptop 7 are the two models Microsoft names specifically, since they’re the highest-volume ARM64 devices currently shipping.

Workaround vs Rollback vs Waiting: Which Should You Pick?

Update the Store package first — it’s reversible, official, and doesn’t touch your security patches. Only roll back if that fails and you need Teams working today.

Two of the three options here don’t cost you any security coverage. Only the rollback does, and only until you reinstall the patch.

When Will Microsoft Ship a Permanent Fix?

There’s no date yet. Microsoft’s release health dashboard lists the issue as “Mitigated” as of September 1, 2026, 19:20 PT — mitigated through the Store workaround, not resolved through a Windows update — and says only that a fix is planned for “a future Windows update.”

When I compared this case against how Microsoft handled a nearly identical Teams/Outlook crash tied to KB5094126 earlier in 2026, the pattern was the same: Store-side mitigation first, cumulative-update fix weeks later. That’s worth knowing if you’re deciding whether to wait it out.

Is Your Windows 11 PC Even Running the Affected Build?

Not every Windows 11 machine is at risk — you can rule this in or out in under a minute before trying either fix method.

Step 1: Check your architecture

Go to Settings > System > About and look at “System type.” If it says ARM-based PC, you’re in the affected group. x64-based PCs are not.

Step 2: Check your OS build

On the same About page, confirm the OS Build reads 26100.9168 or later. Earlier builds haven’t received KB5121003 yet, so the crash shouldn’t apply.

Step 3: Confirm which apps are actually crashing

If it’s specifically the new Teams and the new Outlook — and not Word, Excel, or classic Outlook — that matches this exact bug rather than an unrelated app problem. A handful of forum threads on the Microsoft Community Hub describe near-identical symptoms this way, which is one reason Microsoft moved fast on a workaround.

You’ll probably notice this only on newer Surface hardware bought in the last year or two — older ARM devices running earlier Windows 11 builds haven’t picked up KB5121003 yet through normal update rollout pacing.

Tips

• Check your build number before troubleshooting: Settings > System > About. This bug is tied to OS build 26100.9168 specifically.
• If you manage multiple Surface devices, push the Store update via Intune or Company Portal rather than asking each user to do it manually.
• Bookmark Microsoft’s release health page for this build — it updates in place when the permanent fix ships, so you don’t need to keep re-searching.

Warnings

• Don’t uninstall KB5121003 without pausing updates afterward — Windows Update will silently reinstall it and the crash returns.
• A factory reset will not fix this. The bug is in the update itself, not your device’s configuration, so a reset just reintroduces the same broken state.
• If you’re on a managed/work device, check with IT before uninstalling any security update — some organizations block manual rollbacks entirely.

FAQ

Does this bug affect Intel or AMD Windows 11 PCs?

No. Microsoft’s advisory names ARM-based devices specifically — Surface Pro 11 and Surface Laptop 7 are the confirmed models. x64 machines have not shown this crash pattern in reports so far.

Will updating the Auto Super Resolution Package break anything else?

No reports of side effects have surfaced as of early September 2026. It’s a Store app update, not a system-level change, so it doesn’t touch your Windows security patch level.

Is classic Outlook (the older desktop version) affected by KB5121003?

No — Microsoft’s advisory specifically excludes classic Outlook, Word, and Excel. Only the new Teams client and the new Outlook for Windows are impacted.

Sources

• Microsoft — Windows 11, version 25H2 known issues and notifications
• The Register — Microsoft update disarms Outlook and Teams on Arm PCs
• Windows Report — KB5121003 leaves ARM64 users without Teams and Outlook

This page covers a known Windows 11 issue as tracked on Microsoft’s official release health dashboard. Not affiliated with or endorsed by Microsoft. Fact-checked against primary sources listed above — last verified September 3, 2026.