If your system files are corrupted, built-in Windows 11 components, such as Windows Security, will not be able to run.
When certain prerequisites are not met, the “Enroll Now” option may not appear in Settings → Windows Update on Windows 10.
If you encounter Event ID: 7043, The Windows Security Service did not shut down properly after receiving a preshutdown control in the Event Logs of your Windows ...
Microsoft says the25 Windows security updates are causing smart card authentication and certificate issues due to a change designed to strengthen the Windows Cryptographic Services.
Microsoft's ESU program provides security updates for Windows 10. You normally just head to Windows Update to register for the program. If the option doesn't appear, there are ways to trigger it.