How do you restrict the number of times a youtube video is played in qualtrics?

Hey camilapinto ,
Likely what you want to do is set a timer on the page to either not allow forward advancement or auto-advance the screen. If you don't want them to navigate back and watch again, you would also need to restrict them from doing so.
Here is a YouTube video that illustrates the timing method.
Adding videos to your Qualtrics survey and an introduction to question timings