Microsoft rolls out emergency fix for blocked Windows logins

Microsoft says a Windows 11 update released in late August is blocking customers from signing in with newly added Microsoft Account users after restarting or logging off systems running Windows 11, version 21H2.

"After installing KB5016691 and adding a new Microsoft account user in Windows, you might be unable to sign in for a brief time after the first restart or sign out. The issue only affects the newly added Microsoft account user and only for the first sign in," Microsoft explained.

"This issue only affects devices after adding a Microsoft account. It does not affect Active Directory domain users accounts or Azure Active Directory accounts."

Microsoft says it addressed this issue via Known Issue Rollback (KIR), a Windows capability designed to revert buggy Windows non-security fixes pushed through Windows Update.

Once rolled out, KIR-issued fixes usually reach all consumer and non-managed business devices within a day. Affected users can also get the fix after restarting any impacted Windows devices.

As a workaround, those experiencing this issue can wait for the lock screen to appear again, as it will resolve itself after some time, allowing users to log in as expected. 

Group policies available for enterprise

As an IT admin, you must install and configure a KIR Group Policy to resolve this known issue on affected enterprise-managed devices.

"The special Group Policy can be found in Computer Configuration -> Administrative Templates -> KB5016691 220722_051525 Known Issue Rollback -> Windows 11 (original release)," Microsoft added.

You can download this Rollback Group Policy for Windows 11, version 21H2, from here.

To deploy the Known Issue Rollback via Group Policy, you have to go to the Local Computer Policy or the Domain policy on your domain controller using the Group Policy Editor to choose the Windows version you need to target.

Detailed information on how to deploy and configure KIR Group Policies can be found on Microsoft's support website.

In July, Microsoft issued another emergency fix via Known Issue Rollback (KIR) to address an issue causing the Windows 11 start menu to malfunction after installing recent updates.