Hi, I'm Greg, an installation specialist, 10 year Windows MVP, and Volunteer Moderator. If you will work with me I will be here to help until the issue is resolved.
You can manually update Defender as shown here:
https://www.microsoft.com/ko-kr/wdsi/definitions
Check which version you have of Windows 10 at Settings > System > About. One fix for Updates problems that also brings you to the latest version which includes all of the latest Updates, is to manually Upgrade to the latest version by installing the Media Creation Tool from this link http://windows.microsoft.com/ko-kr/windows-10/m... choose Download Tool Now, install the tool, open it and choose Upgrade this PC Now. This will save your files and apps while bringing you up to the latest version by the most stable method.
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If you prefer to try to fix Windows Updates failure:
- Run the Windows Update Troubleshooter from Windows Settings > Update & Security > Troubleshoot.
- There is a new guided walk-through from Microsoft for repairing Windows Update that leads up to resetting components if necessary: https://support.microsoft.com/en-us/help/10164/.... Try running that first.
- Type Services in Search box, run Services app as Administrator, open Windows Update Service and Stop it.
Press “Windows (flag) key + R,” copy and paste C:\Windows\SoftwareDistribution\ press the Enter button.
This folder has all the files related to Windows updates.
Open the “Download” folder, select all the files and delete all the files.
Restart Windows Update service in Services app by opening it and choosing Start.
- If that fails try manually resetting Windows Update Service:
Open administrative Command Prompt and type following commands one-by-one followed by Enter key.
net stop wuauserv
net stop cryptSvc
net stop bits
net stop msiserver
Ren C:\Windows\SoftwareDistribution SoftwareDistribution.old
Ren C:\Windows\System32\catroot2 Catroot2.old
net start wuauserv
net start cryptSvc
net start bits
net start msiserver
Close Command Prompt and see if Windows Updates works then
- You can also install the Updates manually that fail to install, which are logged at Settings > Update & Security > Windows Update > Installed Update History, and then search for those to download and install from this Catalog: https://www.catalog.update.microsoft.com/Search...
I hope this helps. Feel free to ask back any questions and keep me posted. If you'll wait to rate whether my post helped you, I will keep working with you until it's resolved.
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Standard Disclaimer: There are links to non-Microsoft websites. The pages appear to be providing accurate, safe information. Watch out for ads on the sites that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the sites before you decide to download and install it.