after effects problem

so i had ae for a long time but only recenetly learned how to use it, i was using it for a week and there were no problems. yestreday when i wanted to try new effects with a random video i noticed that when i play it i can only see a black screen but can hear the audio good.. i tried finding sultiouns but couldnt find nothing i even redownloaded it and it still has this problem! PLEASE HELP ME btw i use pc