If a serve is hit over the net and is not returned by the receiver, what is that called?

When a serve is hit over the net in the correct box it is consider good, and/or playable. When not return by the receiver the point would be done and the server would win the point. If the receiver  did not make contact at all with the ball then it would be considered an ace

I believe your final answer would be... Ace , that is if I am understanding your question correctly