If you see an error message that says "There was an initilization error" when opening either DVD Player.app or ProPresenter for Mac, it means that another application is already open and controlling the DVD player. This can be caused by having two copies of ProPresenter open or by having Apple DVD Player open before launching ProPresenter. Close both applications and relaunch the one that you need to use.
This article deals with our legacy product, ProPresenter 6. For the ProPresenter 7 Knowledge Base, click HERE.