A little bit of custom code has to be in place to get this to work. You can see this in use on my site.
View the “Children” collection page template.
https://preview.webflow.com/preview/nd-heart-gallery?preview=391dcc9cdfaacd82261d1038f69a9edf
By looking at the collections and the custom code, you should be able to duplicate that on your site.
I believe I used this post to help me: