Problem with multiple input.getkey

H everyone, I´m developing a game in which you can jump while running and attacking, the thing is that the code doens´t work on some notebooks, I mean, if I want to jump while running (which requires three Input.GetKey at the same time) I can only do it while running left . As I said before, this only happens in some computers, I´ve been reading about it and it so happens that some keyboards can´t handle more than 2 keys been pressed at the same time, Is that correct? I´d really appreciate if you cold help me with this, thanks!!!