Hi @Pdaw123,
Thanks for posting! In order to exclude unfilled customer orders from your review flow, I would advise that you have the trigger for the reviews flow be Fulfilled Order. The next step in the flow should be Wait x days (whichever number of days is the average for the customer to receive their order). The next step would be the review request. This means that any order that is not fulfilled will not receive a review request. As soon as you have fulfilled the order the customer would enter the flow.
I do not know the specifics of your business, so this may not be the best course of action. Let me know if this works and I’m happy to answer any follow up questions!