If a WSUS server fails to obtain updates with the following error: “wsus the request failed with http status 404 not found” this might be because it still uses an old/outdated URL (https://fe2.update.microsoft.com/v6) to obtain the updates from.

This can be checked and changed with the following PS1 Snippet:

$server = Get-WsusServer
$config = $server.GetConfiguration()
# Check current settings before you change them 
$config.MUUrl
$config.RedirectorChangeNumber
# Update the settings if MUUrl is https://fe2.update.microsoft.com/v6
$config.MUUrl = "https://sws.update.microsoft.com"
$config.RedirectorChangeNumber = 4002
$config.Save()
iisreset
Restart-Service *Wsus* -v