Problems using Exify with iCloud Library

When I try to view images in Exify from my iCloud library, I see nothing or experience crashes. What's wrong?

If you have not fully downloaded images from your iCloud library via the Photos app prior to trying to view them in Exify, you may see an empty (black) grid view in Exify or experience a crash. The workaround for now is to open the Photos app and allow these images to fully download before attempting to view or edit them in Exify.