Hello spicygump,
Try this solution by Bill S.
Check the proxy settings.
Internet Explorer, Tools menu
Connection, lan or dialup inteface,
Turn on "automatically detect" or, if you know there is a proxy server
involved, configure it here.
There are other possibilities, but this is the quickest safest thing to try
first.
--
Proxy settings are one source of not updating, but they turn out to be
relatively infrequent, judging by traffic here.
Windows Defender updates by two mechanisms: Automatic updates within the
program to via the AutoUpdate mechanism, or, you can manually go to
WindowsUpdate or Microsoft Update.
On a managed, corporate network, where AutoUpdate is restricted to a
corporate server, Microsoft is providing the definition updates via
WSUS--the administrator must enable the new class of updates. If the
network is running SUS or a third-party solution, automatic update within
the program won't work.
So--check out whether you can get to Windows Update on your machine--if you
can, signature updates should be offered by that route.
There are a few posts from folks with no obvious barrier to updating via
autoupdate who find that updating first via Windows Update allowed for
subsequent autoupdates to work.
