I've recently had to do a clean install of windows 10 and since then I cannot autoplay in youtube. I have unblocked adblocker, I've set autoplay to "on," I've downloaded and reinstalled firefox, installed flash again, but none of that seems to work. I'm having the same problem with South-Park Studios as well; there it simply just doesn't play anything even before my reinstall of windows. Both work in other browsers fine. Only Firefox doesn't work.