well, that's how it's done. so it means your problem is not how to fix location settings has been greyed and i cannot toggle it your problem is you want to force it because your change button apparently doesn't work, which is totally different problem.
anyway, maybe next time you should mention "I clicked change button and nothing happened", is it too hard to explain the problem better?
anyway, it doesn't work by registry, only the toggle, there is a geolocation service you can see if it works. maybe go to msconfig and see if it's checked to start at startup.
and also you can go to group policy -> Computer configuration, Administrative Templates, Windows Components, Location and Sensors, Windows Location Provider
and see if it's enable or disabled there.
good luck.