I know this would be somewhere in your instructions, but I find it strange that the embed link is visible in one post but not a new post.
see attached screen cap
How do I embed a youtube vid in a blank template? and why is the embed video link not in view? if I click the media link it has no option that was obvious to place the desired link in "
https://www.youtube.com/watch?v=WtbPiYQDNkY"
Strange UX guys