Thank you for contacting Aspose support.
Please note, your provided snippet isn’t executable therefore I have modified it as follow. Also attached is the resultant spreadsheet which shows how chart points have been modified with this code. Please note, the latest version of Aspose.Cells for .NET is 16.11.3 which I have used for testing purposes.
Dim sheet = book.Worksheets(“Sheet1”)
For Each objChart As Chart In sheet.Charts
For Each series As Series In objChart.NSeries
For p As Integer = 0 To series.Points.Count - 1
Dim objPoint As ChartPoint = series.Points§
objPoint.Area.FillFormat.FillType = Aspose.Cells.Drawing.FillType.Solid
objPoint.Area.FillFormat.SolidFill.Color = Color.Red
objPoint.Border.IsVisible = True
objPoint.Border.IsAuto = False
objPoint.Border.Style = Aspose.Cells.Drawing.LineType.Dash
objPoint.Border.Color = System.Drawing.Color.Blue
objPoint.Border.Weight = Aspose.Cells.Drawing.WeightType.WideLine
book.Save(dir & “output.xlsx”)