Problem with playung video

I have been having this problem lately to the point of not being able to edit videos, the video does not playback, the audio would play just fine while the video would either freeze on the first frame or repeatedly play a small clip of the video forever while the audio goes on. This meant that I have no way to view my videos so I cannot edit any videos. When I first import the footage, It works fine for like 2 seconds until it start to have the problem. I'm not sure if it is the way I imported the footage, as I would just drag and drop it onto the timeline but I did try every other way and none of them works. Or maybe is a setting I accidentally selected which broke it.