Related field doesn't show the data
I've created a form with a field that should display data from a different table. The relationship is displayed in the attached graphic. The field "Product" in the table "Lessen" contains a numeric value that corresponds with the "ProductID" key of the "Producten" table. I expect that when I choose to display data the following data: "Producten::Naam" that the field shows the value for "Naam" that corresponds with that value for that "ProductID" from "Producten".
But it does not, and stays empty. Could there be anything wrong in the way I've set up the relationships?