I just replaced display, but now it will not turn on; why?

I replaced my macbook air screen because it had a cracked LCD. I replaced the entire display using an ifixit guide, but now when I try to turn on my laptop, I hear it waking up when I have it plugged in and I try pressing the power button, but the screen is black and stays black. How do I know if I made a mistake with the logic board, or with assembly in general, or if my replacement display is faulty? The fan does opperate when I hold down the power button.