I assume this is in the Generate Requisition List process
Perhaps you have inadvertently performed a Change Display Element to Data Element, in which case the flow will not be created. The solution would be to right-click again and select the opposite action Change Data Element to Display Element. See a discussion on the difference between a a display representation and a data representation of the same.
If that is not the solution, I suggest you post a screenshot of the problematic model.
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