Embed Code Generator
The WordPress Visual Editor strips most HTML markup, including the markup used for many embed objects. In order to successfully insert the code from the Embed Code Generator, you need to paste the code into the Text Editor.
Please note that if you switch back to the Visual Editor at any time, WordPress will strip the HTML and you’ll need to paste it again. This is a WordPress “feature” and not a problem with the embed code.
One workaround is to use a plugin such as My Shortcodes or Shortcoder that allows users to create a code snippet that can be embedded in any post using a short code. This will allow you to switch back and forth between the Visual and Text editor screens without affecting the embed code.