My issue is similar in that I have posted videos to a column several time previously and just now trying to post and the video is not displaying in place of the featured image. Not sure what I have forgotten?
Thanks for posting. What we understood from this, looks like it’s not a theme issue. When you face such an issue, can you check and verify if the video is up on YouTube/Vimeo? Also if you can share a screenshot, it would help us to further investigate.