Sharing not showing progress, error, or producing a file

Using iMovie 10.4.3 on a new MacBook Air running Sequoia 15.4.1.

I am trying to export my project for upload on YouTube. It plays fine. I press the share button and choose the social platform button, then set the filename, and have it save to Movies. Then nothing happens. There is no progress bar. No error. And no file shows up in my movies folder.

https://www.youtube.com/watch?v=rnE2dAqKN40