There is a fix for the update error code on this board

[Guest]

Scroll down to the post titiled "How to manually download the latest
definition updates for Windows Defender in Spyware Signatures. I followed
the link to a Microsoft page, and saved the download, ran a virus scan, that
came up clean, and the ran the download. My Defender is again up and
running.

 

[Dave M]

....while I understand your frustration, you've not told anyone what update
error code your encountering, and there are many possible errors. Nobody
that's remotely capable of leading you to a solution in here can help you
without that information. At least I'm glad you found a solution that
worked for your error, whatever it was.