Yeah, it doesn't let me either. I use VLC player from Google Playstore to perform basic functions, and it has the ability to play many files that aren't supported by Samsung.
It changed in inbred of the update. When you open up the video from the gallery, hit the 3 fits and then open in video player. This week asks you to rewind and fast forward through the video as week as tap the video to pause it. You will have to do this each time you watch a video.
