Activating the game on different operating systems.

Problem solved: I was an idiot. It turns out I had two accounts on the forum, and I was entering the login details for the other one. I have no idea when I managed to create a second account... I just have two standard usernames and one standard password. I tried the second username out of curiosity, and it turned out that there were indeed two accounts. That's what happened. Sorry for the inconvenience, please delete the thread.