No.
The Reformation started in 1517. Contrary to popular belief, people in the Middle Ages already knew the earth was round. One of the basic textbooks of mediaeval times was the Almagest, that explicitly said this. Most leaders of the Reformation were well educated and would be aware of this, and the first circumnavigation of the world occurred in 1522 when Magellan's fleet limped into Europe. I am unaware of any statement to this effect by any Protestant leader of the Reformation, and seeing that the "flat earth" is a more modern infatuation of certain literalists, I doubt they would have thought it required to repudiate it.