This article offers some good points of why professional development may not be transforming learning. First, everyone (staff, administrators...etc) needs to realize that the purpose of professional development is mainly to improve student learning (via improving the teachers' craft).
In order to have an impact on student learning, there must be a culture for learning, shared vision between all stakeholders, and buy-in across the board.
One way to accomplish goals of professional development is offered in the book School Culture Rewired. If a culture for learning is developed, the other keys to effective professional development will fall in place.