I'm trying to figure out why my Pro Gallery will not display all content connected to my CMS?

CONTEXT: This is for my personal website with a portfolio of my work. I have a Pro Gallery that is currently displaying 20 images that are connected to a CMS. When clicking on one of the images, it brings you to a CMS-controlled page with more information about that project.

THE PROBLEM: This workflow has worked great for me, however, I’m now adding more work to the CMS and the Pro Gallery is not auto-populating after 20 items. If I re-order the items in the CMS, it will display the new work in the Gallery but does not display work that was bumped below line 20. So this tells me there isn’t an issue with the new work I added. The Pro Gallery is simply not populating more than 20 items. Does anyone have any ideas why this might be happening?

MORE INFO:
The Pro Gallery is formatted to a fixed grid layout.
Scroll direction: verticle
Thumbnail size: Cropped 16x9
Set images per row: 4
Spacing: 2
Load more button: off (but I tried turning this on and it didn’t solve anything)