Error: "Not a valid video file" | YouTube URL on a video post

Entering a YouTube URL in the Attach Media field in the Publisher or Content Calendar is not currently supported. Instead, you can either use a video link other than a YouTube video link, or upload the video file from your computer into the post. 

If you want to log your interest in an open engineering improvement task to explore whether such functionality is possible in a future release, file your request in the Ideas Exchange at ideas.omniture.com.