YouTube videos not embedding

I'm running a self-hosted WP and having problems embedding YouTube videos in my posts. When I preview a scheduled post, there is a large white space where I'm expecting to see the embedded frame, but no embedded content or any sort of border/frame that would indicate that there is content there.

I've tried both copying the YouTube embed video code from the YouTube page as well as simply posting the youtu.be link on a standalone line (which I believe should auto-embed the link, right?).