Based on the 2nd screenshot (which shows izdelek with a red background) I'm guessing the validation error refers to the izdelek display element, probably because you meant it to be an ancestor reference (signified by a blue frame, instead of the standard black).
The validation error you quote occurs when a data element (be it a data structure or a display) is used in a process (action/service) with no incoming flow and therefore will not be created.
The only case where it makes sense to have a data element with no incoming flow, is when the element (usually a display-data element) refers to another one (usually the actual display element), with the purpose of reading data previously entered by the user (or another process) - see stage 3 of the step-by-step tutorial (@ http://www.tersus.com/#Id=2647), for an introduction to this concept
To change the type of izdelek to an ancestor reference do one of the following:
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