Are you seeing a blank space where a video should be displayed? If so, don't panic! There's an easy fix for this problem.
In a book, as in this example, or in a label, you might think that your embedded video is missing....
It's still there! To find it, open the text box in edit view, then click on the "Show more buttons" toggle on the left of your toolbar:
Click on the HTML icon in the lower right corner to reveal the embedded code for the video. Insert an "s" after the http to reestablish the link, click on the HTML icon again (or on Update, if you're using the TinyMCE text editor) to show the video player.