Running macro in PowerPoint slideshow does not run unless done manually first - vba

Question

I'm creating a slideshow to display some stats from a sql table. The macro does not want to run unless I run it manually once so I created a simple test to see if it was something with the sql call. Doing this in PPT 2016.
New presentation with 3 slides, a "title page" and two for data. Created a text box on slides 2 & 3. Saved as .pptm
Sub OnSlideShowPageChange()
Dim i As Integer
i = ActivePresentation.SlideShowWindow.View.CurrentShowPosition
If i = 1 Then Call ChangeData
End Sub
Sub ChangeData()
If ActivePresentation.Slides(2).Shapes("TextBox 1").TextFrame.TextRange.Text = "Answer 1" Then
ActivePresentation.Slides(2).Shapes("TextBox 1").TextFrame.TextRange.Text = "Answer A"
ActivePresentation.Slides(3).Shapes("TextBox 1").TextFrame.TextRange.Text = "Answer B"
Else
ActivePresentation.Slides(2).Shapes("TextBox 1").TextFrame.TextRange.Text = "Answer 1"
ActivePresentation.Slides(3).Shapes("TextBox 1").TextFrame.TextRange.Text = "Answer 2"
End If
End Sub
Close the presentation. Open presentation and run the slideshow. It cycles through the 3 slides and repeats as I want but the "data" is not changing. Esc slideshow and manually run the ChangeData macro. Start slideshow again. Now it cycles through the slides and changes the data as desired.
Any ideas as to why it requires a macro to be run first? I would like to go straight to the slideshow or better yet use the ppt viewer.
Edit:
After looking around more I found this thread How do you run vba code when changing slides in powerpoint?
So, added an ActiveX TextBox and moved off slide with the following code for the control
Private Sub TextBox1_Initialize()
End Sub
Interestingly on the test presentation I have to click on the title slide to kick off the slideshow but when I include the control on my actual presentation it works just fine, without having to click on the first slide. I also tested saving my presentation as a ppsm and it still works. Can modify the sql data and it updates the slide table as desired.
I incorporated Sam's suggestion of Sub OnSlideShowPageChange(ByVal Wn As SlideShowWindow) and also tested as orig and both work. I also tested by adding an ActiveX Label but that did not work, had to be a TextBox or maybe other but not as a Label.