A Faulty March Update Blocked Microsoft Account Sign-Ins
The chain of events began with the March 2026 Patch Tuesday update, KB5079473, released on March 10, 2026. Following its installation on Windows 11 versions 25H2 and 24H2, a significant number of users found themselves unable to authenticate using personal Microsoft accounts in several applications. The device's internet connection remained functional, yet the system consistently returned a "no Internet connection" error whenever a sign-in was attempted through a Microsoft account.
Applications confirmed to be affected by this defect include Microsoft Teams Free, OneDrive, Microsoft Edge, Microsoft 365 Copilot, and various Office applications. The issue was exclusive to personal Microsoft accounts — organizations relying on Microsoft Entra ID for authentication were not impacted.
KB5085516: The Out-of-Band Fix
On March 21, 2026, Microsoft released an out-of-band (OOB) cumulative update designated KB5085516 to address this sign-in failure. As a cumulative update, it incorporates all previous security and non-security improvements from KB5079473 in addition to the specific fix for the authentication issue. The update targets Windows 11 version 25H2 (OS build 26200.8039) and Windows 11 version 24H2 (OS build 26100.8039). Microsoft has confirmed that no new known issues are introduced by KB5085516.
Who Is Affected and Who Is Not
The sign-in problem affects only consumers and individuals using personal Microsoft accounts on Windows 11 versions 25H2 or 24H2 who installed KB5079473 or a later update. Enterprise environments using Microsoft Entra ID as their authentication provider are not affected by this regression. Users on older versions of Windows 11, or those who had not yet installed the March Patch Tuesday update, also remain unaffected.
Related: KB5079473 — March 2026 Cumulative Update for Windows 10 and
How to Obtain the Fix
For most users, KB5085516 is delivered automatically through Windows Update. Devices running Windows 11 25H2 or 24H2 with KB5079473 already installed will find the update available in the optional updates section. To install it manually, navigate to Settings > Windows Update and select "Download & install." A system restart is required to complete the installation. The update is also available for direct download through the Microsoft Update Catalog for administrators who manage deployments manually. IT professionals using Microsoft Intune or Windows Autopatch can accelerate its deployment using the standard quality update acceleration procedures for those platforms.
Practical Advice and Next Steps
After installing KB5085516 and restarting the device, users should confirm the update has been successfully applied by checking the installed build number in Settings > System > About. The expected builds post-installation are 26200.8039 for version 25H2 and 26100.8039 for version 24H2. If the update does not appear in Windows Update, waiting a few hours and re-checking is recommended, as rollout is gradual. Should sign-in issues persist after installing the patch, restarting the impacted applications and signing in again is the recommended first troubleshooting step.
Since the March 2026 Patch Tuesday cycle, Microsoft has issued multiple out-of-band updates addressing separate regressions. Keeping Windows Update active and periodically checking for optional quality updates remains the most reliable way to stay current and minimize disruption.
