This can happen if the program is running or if the computer is in standby, but ProPresenter was still open. Generally this is caused by disconnecting your external display from your computer while ProPresenter is still open. If you open ProPresenter and the screen immediately goes black (or other solid color), don't worry, this just means your output screen has moved. You open ProPresenter and the screen goes black. The steps below will walk you through each possible scenario first with the fix at the end.
If ProPresenter is hidden behind your Output or Stage Display when you open the program or when you enable one of those outputs, it only takes a few seconds to fix.
