how do i log into facetime. it kicks me out and shows a black screen everytime i try

So i am using my school macbook air. I always used to be able to facetime on it. But all of a sudden everytime i try clicking it, it would show a quick black screen and then go back to the page i was on previously. I Don't know how to fix it, I have updated my computer, gone into settings and looked. I can't figure it out. I would really like to be able to facetime on my computer. Please help me get facetime to work.