To use the meta fields in our app, you must make sure that the meta fields are public and that they are already in the products in the online store. You must make sure that the metafields are configured correctly and are created by a metafields app, otherwise they will not work in our app

You must click on the pencil to edit the product:

You must go to "Caption Content," and there will appear all the meta fields that can be used for that product:

It is worth mentioning that you cannot create meta fields directly in our app.