This is a similar problem to the one you had a couple of weeks ago.
You cannot have the child of a repetitive element as the target of a flow, because there is no way to know which instance of the repetitive element you refer to.
In your case, I guess you want to create an instance of 'Imported_Orders' for each value you get from the service. To do this, you should create a repetitive action that creates instances of 'Imported_Orders'. If you have n output, the action will be called n times, each time creating an instance of 'Imported_Orders'.
The model I sent you a couple of weeks ago contains a few examples of such a modeling pattern.
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