Hi again.

I see that you are calling the function correctly... wondering what could be the problem.

Please check the following:
- Both files ("PRHR MASK_TRAINING PRESENTATION_notes.pptx" and "PRHR MASK_TRAINING PRESENTATION_NOnotes.pptx") are already open and editable (make sure they are not opened as read only).
- The number of slides in each presentation matches and the starting slide number is similar (whether they start with slide #1 or slide #0).

When you enter the debug mode (where the yellow highlight shows up, in your second screenshot), hover your mouse over the "i" in "oSource.Slides(i)....." and it should show you the value of "i", which would be the slide number where the error occurred... this might help troubleshoot in case there's a particular slide causing the issue... if it's 1, that means it's happening in the first iteration, so there is something preventing the script from working...

You may want to also hove over each variable while stopped in debug mode to double check that each of them is loaded properly... that is, "mySource" and "myTarget" (should have the filenames), "oSource.Slides.Count" and "oTarget.Slides.Count" should both have a number (the count of slides in each presentation, that should be similar)...

Let's see if this helps you figure out what the problem is... I'm happy to take a look at your files if you wish, but I understand that sending your content to someone you don't know is not quite recommended