You're well-prepared, but if your launch falls below expectations, what's your next strategic move?

First I'd examine the expectations and assumptions. Of the last 50 launches I've been part of, I have found that people frequently expect a lot more to happen than typically does. A launch most often adds momentum to something that is already working at smaller scale. It does not create the momentum.

Identify why it failed! Fix it re iterate!

before coming up with a new strategy I think it is better is to thoroughly analyze the data and gather insights into what went wrong. Examining sales figures, user feedback, market research, and any other metrics to fully understand where the launch fell short so that we can come up with a even better strategy to reach our expectations.