iMovie photos not updating to reflect iPhoto’s

Another thing that you can try is to delete preferences. To delete preferences, open iMovie while holding down the Option

and Command keys and select to delete preferences in the box that appears. iMovie will open in a new library. Reopen your old library to get back to your projects.  Deleting preferences is a safe procedure that will not cause data loss or disruption to your project.

Are you by any chance intending to refer to the Photos app, rather than the iPhoto app? For iMovie to recognize the photos in the Photos app your Photos library must be designated as the system photo library in the Photos app general preferences. The words "use as system photo library" need to be grayed out.

Since iPhoto is outdated and has been replaced by the Photos app, it may be that iMovie no longer links to it. You should be able to update your iPhoto library into Photos, and link that way.

Whether the photos are in the iPhoto app or the Photos app, you can always do the workaround of dragging the photos into iMovie. You can drag them directly from the Photos app, but with the iPhoto app you may first need to drag the photos to your desktop and from there into iMovie.

-- Rich