Excel VBA：可以删除验证但不能添加新验证

My code is as follows

我的代码如下

If Cells(Target.Row, 2) = "" And (Cells(Target.Row, 3) = "" Or Cells(Target.Row, 3) = "") Then
    Sheets("MySheet").Activate
    Cells(Target.Row, 3).Activate
    ActiveCell.Validation.Delete
    If (Cells(Target.Row, 2) = "Type A") Then
        ActiveCell.Validation.Add Type:=xlValidateList, AlertStyle:=xlValidAlertStop, Operator:=xlBetween, Formula1:="=AvailableVersions"
    ElseIf (Cells(Target.Row, 2) = "Type B") Then
        ActiveCell.Validation.Delete
    Else
        ActiveCell.Validation.Add Type:=xlValidateWholeNumber, AlertStyle:=xlValidAlertInformation, Formula1:="0", Formula2:="9999999"
    End If
End If
If Cells(Targe