"New App Preview" not available in iMovie

I want to create an App Preview video for an app. I have started iMovie but no matter what I try the "New App Preview" is greyed out. I created a movie in Quicktime and imported it in...still nothing.

The solution is to Open iMovie. then immediately click "Project" at the top left. This displays all projects if available. Then go to File and under that menu option "New App Preview" is active and can be selected

When you first click on iMovie , don't click the "Create New" button right away, instead click "File" in the menu bar then "New App Preview" as shown in pic below: