Windows 11 KB5124008 Fixes Teams & New Outlook Launch Issues on ARM PCs

Microsoft has finally fixed an annoying issue affecting Teams and the new Outlook on ARM-based Windows devices. The issue had bugged users for several days, as both apps would not launch or would close unexpectedly. But the good news is that the Teams and new Outlook’s launch issue has finally been fixed with latest KB5124008 security update.

Teams and Outlook users were affected on ARM-based PCs

The issue first stemmed from Windows security update, KB5121003, released on August 11, 2026. At the time, Microsoft confirmed that affected devices included ARM-based PCs such as the Surface Pro 11 and Surface Laptop 7.

The issue was most likely affecting new or freshly imaged PCs, as these systems had not yet installed Microsoft Store updates, which appears to have played a role. Thankfully, the problem was limited to specific applications. At the time, Microsoft shared a workaround and said that Classic Outlook, Word, Excel, and other applications were not affected by this issue.

Microsoft has fixed the Teams & Outlook launch issue with KB5124008 September 2026 patch

Microsoft has confirmed the issue has been fixed via Windows 11 September KB5124008 Patch Tuesday update released on September 8, 2026. If you have already installed KB5124008 or a newer update, you do not need to apply the previous workaround. Microsoft recommends installing the latest available Windows update for your device.

The issue affected Windows 11 versions 26H1, 25H2, and 24H2 on client devices. There were no affected Windows Server platforms listed. So, if Teams or the new Outlook suddenly refused to launch on your ARM PC, the latest Windows 11 update should finally put your headache to rest.