Hi @colevalleygirl the light box needs a link to open. It will not work on an embedded video. I’m not sure if it was possible with the Classic Editor to paste a URL and make it a link instead of letting it be converted to an embedded video.
In the new editor this is fairly easy: after pasting the URL on a new line, it will convert to an embedded video block but you can change the block to a paragraph block with a linked URL. In the old editor it might not be so easy.
A possible work-around to prevent the embedded video from appearing: First type some text (or even a space) and then paste the URL on the same line not a new paragraph! Or better: type the title of the video, then select the title and click the “Insert/edit link” icon. Then paste the URL there to make it a link.
The link itself will be detected by Easy FancyBox and will open in a light box.