Retrive object by assosiation is null

Hi experts,  as soon the button "Zusatzinformationen" is checked I create an object of the type "Dokument_Zusatzinformationen" with a microflow.  Users then can pass information to the interface, I want to use this information to call a REST service, therefore, I want to receive the object which holds the data provided by the user of the type "Dokument_Zusatzinformationen" in another microflow ( the one who calls the rest service) but somehow the object is empty(null). So this means that I received an object which doesn't exist at this point?  It is no problem to call the rest service with the information provided without the entity (input_document entity). I don't receive the information from the entity which is created (create_Zusatzdaten) when I activate the checkbox information.      
1 answers

Do you have a change object action in your Create_Zusatzdaten microflow that sets the association between Imput_Document and Dokument_Zusatzinformation on the Input_Document object? If not, you only create the Zusatzinformationen object but never associate the two.