Activation error DISM on Windows Server - could not activate

Ever tried to activate an Eval download of Windows Server and got an activation failure? Or got an error 50?

The command most commonly referred to online and in Microsoft guides is as below:

Firstly, make sure your version is actually genuine and you're licensing the right version too.

Run the following command:

DISM /online /Get-TargetEditions

This will reveal what you can upgrade Eval too, in a majority of cases we'll use Server Standard as an example but this refers to datacenter too.

Run the below to license your server:
DISM /online /Set-Edition:ServerStandard /ProductKey:XXXXX-XXXXX-XXXXX-XXXXX-XXXXX /AcceptEula

If this still doesn't work, something that I spent hours of my life one evening figuring out... is that a command window that isn't elevated will produce an error 50, unknown error and/or a activation couldn't be completed.

Yes, its truly that simple! Elevate Command Prompt and try again, 9/10 this will fix the issue for you!