Cannot trigger macro with Worksheet_Change(ByVal Target As Range)

Hello,
I am not capable to make any Worksheet_Change(ByVal Target As Range) macro works. I tried several of them and none of them works in my Excel 2010. I boiled it down to the simplest version below, I studied several different treads on this forum and still nothing works. Any help is greatly appreciated.

Private Sub Worksheet_Change(ByVal Target As Range)

If Target.Address = "$A$1" Then

MsgBox "the macro works"

End If

End Sub

The file is attached - again it simplified to single page, one cell which should be monitored by the macro.