When I try to sort the photos (I have 382), I can only see two rows in the photo sorter view. I have zoomed all the way out and only see two rows. There is room for at least two and maybe three more rows.
I am using Magix Photostory Deluxe v 126.96.36.199 (UDP3). It says Code UG 8657 KA4.
Check how many images are on the timeline - the screenshot you have posted would indicate that there are only 30 images on the timeline, also the view is not zoomed all the way out as can be seen below.
After I posted and sent in a bug report, I did some further testing just in case there was an issue with graphics drivers - nothing found and changing to the different display modes in the program settings made no difference either.
One test I did was to add an extra batch of images when in the slide sorter - you can see the images loading and then they disappear except for the last one added - odd 😕.