VBA: getting rid of GapWidth in Combo Chart (Lines + Clustered Columns) does not work

Question

I am using VBA for ppt deck populating (using template) and I am not able to get rid of Gap Width for one data series in Combo Chart. Chart includes lines for avg prices (primary axis), clustered columns for units (secondary axis) and clustered column for Period (primary axis), where I am trying to use GapWidth = 0 that should serve just for highlighting the period. Please note I am talking about visualisation, not data missing problem or data==0 problem. This is how data looks like (dummy data):

Date	Period	Avg Price	Units
04/05/2019	0	10	21
05/05/2019	0	9.5	26
06/05/2019	1000	7.0	43
07/05/2019	1000	7.0	47

I am using below lines, but it is completely ignored. Could someone please help? Thank you!

newPpt.Slides("ItemsPrice").Shapes("Items_price_chart").Chart.FullSeriesCollection(1).ChartType = xlColumnClustered
newPpt.Slides("ItemsPrice").Shapes("Items_price_chart").Chart.FullSeriesCollection(1).AxisGroup = 1
newPpt.Slides("ItemsPrice").Shapes("Items_price_chart").Chart.FullSeriesCollection(1).Select
newPpt.Slides("ItemsPrice").Shapes("Items_price_chart").Chart.ChartGroups(1).GapWidth = 0

With Selection.Format.Fill
    .Visible = msoTrue
    .ForeColor.ObjectThemeColor = msoThemeColorBackground2
    .ForeColor.TintAndShade = 0
    .ForeColor.Brightness = 0
    .Transparency = 0
    .Solid
End With