If you open ProPresenter and you can't see your mouse cursor, this is likely due to your Output screen being assigned to your main computer screen. This may have happened if you disconnected your external displays from your computer while ProPresenter was still open.
To fix this, press Control-1/Command-1 to turn your Output off. When you do this, you should immediately have full control of your cursor again. Click on the ProPresenter menu, then on Preferences. Go to the Display tab.
Take a look at the boxes on this tab. If the word "Out" is assigned to the same box that has a thick white bar across the top, then you need to reassign the Output. Click on the word "Out" and drag it to the box that represents your normal output screen. Once you have reassigned the Output, you can press Control-1 to turn your output back on.