Code Issue With Save Prompt Not Saving

I've been having issues saving changes in my workbook as of late, and discovered that this bit of code seems to be faulty:

Private Sub Workbook_BeforeClose(Cancel As Boolean)
    Dim lngResp As Long
    If Not ThisWorkbook.Saved Then
        ThisWorkbook.Saved = True
        lngResp = MsgBox("Do you wish to save the workbook before closing?", vbYesNo)
        If lngResp = vbYes Then
            With ThisWorkbook
                 .Save
                 .Saved = True
             End With
        End If
    End If
End Sub

..for when I make changes to the workbook, and then just close it without saving manually, I get this message:

Do you wish to save the workbook before closing?

..and upon choosing 'Yes', the workbook closes, but no changes are saved. What could the error be? I've attached a sample of my workbook below.

And for reference purposes, here is where this code originated.