Autogroup not working in pivot

[Balajibenz]

I have below lines of code whare i am trying to group the dates in to month. below code is not grouping and at the same time not throwing any error.

can someone help me with this.

With ActiveSheet.PivotTables("Report").PivotFields("WEEK_END_DATE")
.Orientation = xlColumnField
.Position = 1
End With
'ActiveSheet.PivotTables("Report").PivotFields("WEEK_END_DATE").AutoGroup

WEEK_END_DATE column is formatted in "dd/mm/yyyy". I am able to group it manually in pivot.