Try using source code screen in editor and copy youtube -share -embed code instead. see sample code.

--<iframe allowfullscreen="" src="https://www.youtube-nocookie.com/embed/kP9TfCWaQT4?rel=0" alt="kP9TfCWaQT4?rel=0" width="560" height="315" frameborder="0"></iframe>
</p>--