Since August 29th, many users have reported various login problems on Windows 11 and Windows Server 2025, and that includes both Windows 11 24H2 and the newer Windows 11 25H2. According to Microsoft’s support page on the issue , the issue is caused by new security protections that are unfortunately causing Kerberos the authentication protocol in Windows and New Technology LAN Manager NTLM to fail for users with duplicate Security IDs SIDs. The issue can start occurring on relevant syst
