Windows defender virus & spyware definition not updating
Run the Microsoft "Fixit" application.
When you use the Windows Update website or the Microsoft Update website to check for and install updates, you may receive one of the errors that are listed in the "Symptoms" section.
Windows 8.1, Windows 8 or Windows 7
The Automatically diagnose and fix common problems with Windows Update
troubleshooter may automatically fix the problem described in this
There is a link on the page to Microsoft Fixit - the
run now button
When you use the Windows Update website or the Microsoft Update
website to check for and install updates, you may receive one of the
following error code in the error messages:
0x8024402C -2145107924 WU_E_PT_WINHTTP_NAME_NOT_RESOLVED
These errors may be caused by any of the following issues:
- Programs or processes that interfere with Internet communications
- Resource issues on the computer
- High Internet activity
- Recoverable database errors
Source Temporary connection-related errors may occur when you use Windows Update or Microsoft Update
Additional troubleshooting steps
If the above doesn't fix your issue, then see How to solve connection problems concerning Windows Update or Microsoft Update.