change font in PPT text box from VBA

I'm trying to change the font of an empty text placeholder on a slide from VBA. Sounds simple enough but apparently I haven't got the right object or something...

I've tried a variety of approaches including the ones shown below. Test1 (textrange object) and Test2 (shape object) didn't work. Then I used the macro recorder to record the UI actions that do accomplish what I want. However, replaying this macro does *not* cause the correct result.

What am I missing?

Thanks

Sub test1()
    Dim tr As TextRange
    
    Set tr = ActivePresentation.Slides(1).Shapes(2).TextFrame.TextRange
    tr.Font.Size = 18  
End Sub
Sub test2()
    Dim shp As Shape
    
    Set shp = ActivePresentation.Slides(1).Shapes(2)
    shp.Select
    ActiveWindow.Selection.ShapeRange.TextFrame.TextRange.Font.Size = 18
End Sub
Sub Macro12()
    ActiveWindow.Selection.SlideRange.Shapes("Rectangle 21").Select
    ActiveWindow.Selection.ShapeRange.TextFrame.TextRange.Font.Size = 18
End Sub

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