Auto Insert Row But Column Q Formula Not Working

I have code for auto insert row, when i m getting to new row column Q formula not working

remove the auto generate serial number in column column A, only i want to insert auto with column Q formula to work.

find enclosed a worksheet for your ref.

Please see the below auto insert code;
Private Sub Worksheet_Change(ByVal Target As Range)
Dim O As Range
Set O = Range("O:O")
If Intersect(Target, O) Is Nothing Then Exit Sub
Application.EnableEvents = False
roow = Target.Row
Cells(roow + 1, 1).Value = Cells(roow, 1).Value + 1
Cells(roow + 1, 2).Select
Rows(Target.Row + 2).Insert
Application.EnableEvents = True
End Sub