Sub TestCode()
'Declare
Dim oPA As PowerPoint.Application
Dim oPP As PowerPoint.Presentation
Dim oPS As PowerPoint.Slide
Dim oShape As PowerPoint.Shape
Dim oPicture As PowerPoint.Shape
 
'Set path and fielname of existing PowerPoint
'ExistingPPT = "Libraries\Documents\Test.pptx" 'make sure presentation has one blank slide.
 
'Set path and filename of picture to be imported into ppt
MyPicture = "Libraries\Documents\Tara1.jpg"
 
'Open Existing PowerPoint
Set ppt = CreateObject("PowerPoint.Application")
With ppt
    'Open existing PowerPoint (THIS BLOCK WORKS)
    .Visible = True
    .Presentations.Open (existingPPT)
    .ActiveWindow.View.GotoSlide (1) 'this line makes testing easier otherwise not required
 
   'Add Picture (e.g. import it into PPT) (THIS BLOCK DOES NOT WORK)
    Set oShape = oPS.Shapes.AddPicture(MyPicture, msoFalse, msoTrue, 1, 1, -1, -1) '(Filename, LinkToFile, SaveWithDocument, Left, Top, Width, Height)
 
   'Size Picture
    Set oPicture = oPS.Shapes(oPSe.Shapes.Count)
    oPicture.ScaleHeight 1, msoTrue
    oPicture.ScaleWidth 1, msoTrue
    oPicture.LockAspectRatio = True
    oPicture.Width = 750 '750 is arbitrary
 
   'Center picture
    With oPA.ActivePresentation.PageSetup
        oPicture.Left = (.SlideWidth \ 2) - (oPicture.Width \ 2)
        oPicture.Top = (.SlideHeight \ 2) - (oPicture.Height \ 2)
    End With
End With
 
End Sub