Hi again Jess!
I’ve looked again at your site, both in live and preview and it seems like its working for me.
Here are some screen shots of my side:
As for not showing in the “sandbox”, that was my bad, you don’t need the items to be on both collections.
Live collections for items that are uploaded from the live site, sandbox for items from preview mode or added directly to the collection.
Try to refresh your browser while viewing the gallery page (on live site).
Let me know if you’re still facing issues with that.
Doron.