Linking multiple entities and combine on a single page in a Data view

Hi all! I want to add an attribute from a different entity to an existing page. On this page, I have a data view with a different entity. In the domain model screenshot you can see how the entities are linked.  I don’t receive an error, but in the preview of the app I don’t get the correct view of the field I want to add. Does anyone know what the problem is there? Thank you in advance for your help!   Domain Model:   Page:
1 answers

Under the creation / due date, I should be able to see a drop-down menu to select the correct value center. But in the highlighted part you can see, that I can not see the drop-down menu.