it seems to be working in software mode 800x600 and compatibility launch in win XP package 3. I made a skirmish.Otherwise it does not work in other graphic modes. A patch is needed maybe for a better graphic resolution on win 8.1. .
I made 2 more campaign mission, well, it seems to be working correctly.

I'd contact Support. If they can't help then you might be eligible for a refund.

Do not worry, this game is working fine in 800x600 win XP compatibility mode on win 8.1. This is one of my favoirte game !!!!! no refund needed especially with such a small price); I had wait a long time to play it again since on the win XP of my precedent computer, the game was not working for me. But now i can play it on win 8.1. I just hope later we can get superior resolutions but i am happy for now. Thanks for your reply. I look forward to get the other games in the franchise.