That's because (if you know Clickteam) they are in .avi files and I used the Active Direct Show object to implement the cutscenes into the game, because I wasn't about to implement them into the game as .gif files (it could be the alternative solution to fix this issue).

As I just said, the cutscenes don't play at all on other computers, leaving only a black screen.

So, in that case, if you have used the Active Direct Show object before in the past to show a cutscene in your game-that only plays on your computer, but it doesn't play on anyone else's computers, how did you fix the issue? Let me know how you fixed the problem in the comments. I'm kinda curious.