Make sure your power cable is plugged in, if not then plug it in.
Make sure your HDMI cable is securely fastened in to the apple tv and into your tv. (You may want to try to use a new cable if it does not work)
On most apple TV's there is a white dot, if it is on, you probably have a faulty HDMI cable.
Open the video in the app, click on "Share", Copy Link, and then paste it into a browser. Then, it should be able to play.