Added video only plays at the beginning of timeline

I am using a 4 second clip on a slide and having so many problems. First of all, it does not add as its original length- researching it I just discovered you have to remove the play until end option when adding a video, which is unintuitive enough. But now it will only play if it is at the start of the timeline. If I move it where I want it to be, I only get a still of the last frame. Super frustrated and on a deadline- Please advise!