It's definitely working here, using your code above in a .bat file.
Check the reg code and path are exactly correct, without any extra spaces at the start or end. The reg code should contain three - characters, separating four groups of five characters.
Using a non-elevated command prompt is best, else Opus will be running elevated afterwards. (But this doesn't seem to affect whether or not the licence installs; it'll just cause other problems.)
If you do keep it elevated, add the /norun argument that's in the example I linked to.