Windows Update error 0x8024401B

 Ah the dreaded error that WSUS throws at you.

There are several "solutions" to be found with a quick Google.

But in my case it was quite clear, on 5 identical machines 1 couldn't access the WSUS server on the network. So what's the difference?

Came across this post on docs.microsoft.com
https://docs.microsoft.com/en-us/troubleshoot/mem/configmgr/troubleshoot-software-update-scan-failures

The portion that stood out was the proxy bit. Checking the current settings on the machine that was working and the machine that wasn't working.

The working machine:

C:\windows\system32>netsh winhttp show proxy

Current WinHTTP proxy settings:

  Direct access (no proxy server).

And the non working machine:

C:\windows\system32>netsh winhttp show proxy

Current WinHTTP proxy settings:

Proxy Server(s) :  http=proxy.domain.lan:8080

    Bypass List     :  *.domain.lan;192.*

And there it was, well that's a quick fix:

netsh winhttp reset proxy