Errors in the WSUS Log File:
“Fatal Error: A required configuration value was not found in the system”
If that happens, you probably used an SQL Database for WSUS and you did not enter the Instance Name in the Wizard box.
Unfortunately, if you leave that field blank, the WSUS Wizard continues assuming it should setup the DB on the Default Instance, however, the PoerShell Command that is beeing executed afterwards expects this parameter to be present in the config file that you actually generate using the wizard.
The Solution is to uninstall WSUS, (maybe also reboot your server) and install it again. But this time enter %yourservername% in the Instance box if you have a default instance present on that Server.