My order is complete, but did the buyer not review?
Some buyer does not want to give a review. You have delivered your work you have done your job do not push the buyer to give you review, he may rate your service negative.
thanks for suggestion
It is up to the buyer as to whether they want to leave a review or not.
If you check the Terms of Service at the bottom of the Fiverr main page you will find the rules as to how Fiverr works.