Hi @charlesr
You need to use a different code to query the posts based on the subfield. This page should give you more idea about it (Under the “4. Sub custom field values” section): https://www.advancedcustomfields.com/resources/query-posts-custom-fields/.
We also have a guide to creating a bidirectional relationship that may fit your setup. Please check this page to learn more about it: https://www.advancedcustomfields.com/resources/bidirectional-relationships/.
I hope this helps 🙂
