ISSUE:

After inserting a YouTube Video design element and using a link for a YouTube video in it, it looks like this in render mode:



REASON: 

Incorrect video link format.


SOLUTION:

Please, make sure you:


1) Copy the video link from the top address bar in YouTube, as shown here:



2) Copy the link of a video on YouTube that is opened separately, outside of a playlist.


That's it! 

Thank you for your attention.