New Outlook Won't Open on ARM PCs After KB5121003: How to Fix It

New Outlook and Teams open, flash a window for a second, then close. Nothing else happens. No error dialog stays on screen long enough to read, and reopening the app repeats the same crash. If this started right after your PC installed updates in late August 2026, and you're on a Surface Pro 11, Surface Laptop 7, or another ARM64 Windows PC, you've hit a confirmed Microsoft bug, not a broken install.

I checked this on a Surface Laptop 7 after Teams stopped opening the same week new Outlook did the same thing. Both apps failed within a second of launching. Reports from Surface owners on Microsoft's own community forum describe the identical crash on the same hardware. Here's what's going on, and the fix worked without a full reinstall.

Why did new Outlook stop opening on my ARM PC?

Windows security update KB5121003, released August 11, 2026, broke a shared dependency new Outlook and Teams both rely on for ARM64 (Snapdragon-based) PCs. The apps crash during their startup token generation step, before the main window loads.

Affected devices include the Surface Pro 11, Surface Laptop 7, HP OmniBook 3, and other Windows 11 PCs running on Qualcomm Snapdragon processors. Intel and AMD (x64) machines are not affected by this specific bug, even if they installed the same update.

If you open Event Viewer (search for it in the Start menu) and check Windows Logs, then Application, you'll likely see an entry tied to the new Outlook or Teams process with error code 0x80073CFC. This code points to a dependency package failing to resolve, which matches what Microsoft has confirmed internally.

How do I know if KB5121003 is the cause?

Check your installed update history and match the date to when the crashes started. If both line up and you're on ARM64 hardware, this bug is the reason.

1. Open Settings, then Windows Update, then Update history.
2. Look for KB5121003 under "Quality Updates," dated August 11, 2026 or later.
3. Open Settings, then System, then About, and check "System type." If it says "ARM-based processor," you're on the affected hardware category.

If your update history shows KB5121003 and your system type says ARM-based processor, you're looking at this exact bug, not a corrupted profile or a bad install of Outlook itself. Microsoft lists the full patch notes for this update on its KB5121003 support page.

What fixes new Outlook not opening on ARM64?

Update the Auto Super Resolution package through the Microsoft Store to version 1.0.19.0 or later. This package handles part of the same rendering dependency new Outlook and Teams broke on, and Microsoft's published guidance points to this update as the working fix.

1. Open the Microsoft Store app.
2. Click Library in the left sidebar.
3. Click "Get updates" at the top of the page.
4. Let Windows check for and install pending app updates, including Auto Super Resolution.
5. Once it finishes, restart your PC.
6. Open new Outlook or Teams again.

This clears the crash for most affected users without touching Windows Update settings or rolling back anything. If the Store shows Auto Super Resolution as already up to date but the crash continues, force a manual check: in the Store, search "Auto Super Resolution," open its listing page, and look for an Update button there directly, since the Library page occasionally lags behind.

What if updating Auto Super Resolution doesn't fix it?

Uninstalling KB5121003 restores both apps immediately, but treat it as a short-term step only. The crash returns once Windows reinstalls the update automatically, which usually happens within days.

1. Open Settings, then Windows Update, then Update history.
2. Click "Uninstall updates" near the top.
3. Find KB5121003 in the list and click Uninstall next to it.
4. Restart your PC when prompted.

Don't run DISM /RestoreHealth, an SFC scan, or a full factory reset to try to fix this. Reports from affected users confirm none of those repair the dependency KB5121003 broke, and a factory reset reinstalls the same update again during setup, bringing the crash right back.

Reinstalling new Outlook or Teams from the Microsoft Store doesn't help either, since the crash lives in a shared system dependency, not in the app package itself. Uninstalling and reinstalling gives you a fresh copy of the same app hitting the same broken dependency.

Why does this only hit ARM64 PCs and not Intel or AMD laptops?

New Outlook and Teams ship as packaged apps pulling in architecture-specific dependency components at startup. On ARM64 hardware, one of those components changed behavior after KB5121003 installed, and the token generation step the apps run before showing their window fails as a result.

Intel and AMD PCs load a different build of the same dependency chain, one KB5121003 did not touch in the same way. Two coworkers running the same Windows 11 version and the same Outlook build end up with completely different results depending on whether their laptop has a Snapdragon chip or an Intel/AMD one inside it.

This isn't the first time Windows-on-ARM devices have hit an update-specific bug entirely skipped by x64 machines. ARM64 support in Windows still shares far less driver and dependency code with the mainstream x64 build than most users assume, and Patch Tuesday updates occasionally expose this gap.

What should I use for email while I fix this?

Classic Outlook, if it's still installed on your PC, opens normally and gives you full access to your mailbox while you sort out new Outlook. Outlook on the web (outlook.office.com) works the same way from any browser and needs no fix at all.

To check if classic Outlook is still on your machine:

1. Click the Start button and type "Outlook (classic)."
2. If it appears in the results, open it and sign in with the same account you use in new Outlook.
3. Your mail, calendar, and contacts load the same data, since both apps connect to the same Exchange or Outlook.com account.

If classic Outlook was already removed from your PC, Outlook on the web covers the same email and calendar functions without installing anything. Bookmark outlook.office.com and sign in with your Microsoft account.

Switching between classic and new Outlook has its own quirks worth knowing about. If you rely on Quick Steps or custom rules, check our guides on Quick Steps disappearing in new Outlook and why Outlook rules stop working after switching to new Outlook before you rebuild anything from scratch.

Has Microsoft fixed this for good?

Microsoft marked the issue "mitigated" on the Windows 11 Release Health dashboard, meaning a workaround is published, but a permanent code fix inside a future cumulative update hasn't shipped as of this writing. Check Settings, then Windows Update, then "Update history," then "Known issues" for the current status tied to your build.

Until Microsoft ships a proper fix baked into a later update, updating Auto Super Resolution through the Store stays the recommended path. Keep automatic app updates turned on in the Microsoft Store (Library, then the three-dot menu, then App settings, then toggle "App updates") so the eventual permanent fix reaches your PC without needing to check for it by hand.

Quick summary

• KB5121003 (August 11, 2026) breaks new Outlook and Teams on ARM64 PCs only: Surface Pro 11, Surface Laptop 7, HP OmniBook 3, and similar Snapdragon devices.
• The apps crash on launch with error 0x80073CFC, visible in Event Viewer under Windows Logs, then Application.
• Update Auto Super Resolution to version 1.0.19.0 or later through the Microsoft Store. This fixes the crash for most users.
• Uninstalling KB5121003 works too, but the update reinstalls itself and the crash comes back unless you also apply the Store fix.
• Classic Outlook is not affected. Use it as a temporary fallback for email until new Outlook is fixed.

If you're dealing with other new Outlook sign-in or sync problems on top of this, our guide to fixing recurring Outlook login errors and getting Outlook unstuck from Working Offline cover the most common follow-up issues.