[mirimir]

> I wanted to give both the anime and the Microsoft Store's video section a try, and did nothing more than just opening the Microsoft Store, finding the content, getting it for free and watching the first episode. My guess is that this might have been the problem.

I agree. It's very likely that, by using a US VPN, you circumvented geo-restriction in the Microsoft Store. You could test that by creating another Microsoft account, under a fake name, using a commercial VPN service with a non-US exit. Then try to get the Dragon Ball Z episode from Microsoft Store. If you need help, feel free to email me.