Welcome to Microsoft Q&A Platform.
In order to improve system’s security and stability, we should install the latest cumulative update.
If you couldn’t install this KB4549951, try the following steps:
1.Run Windows Update troubleshooter.
2.Make sure computer has installed the latest SSU KB4552152.
3.Manually install KB4550945 https://www.catalog.update.microsoft.com/Search.aspx?q=KB4550945, Skip KB4549951
4.If still fail, reset Windows Update components and check for update again https://learn.microsoft.com/en-us/windows/deployment/update/windows-update-resources