unable to load & save a workbook from a VBA function

Here's what I have so far

Option Explicit

Function LRS(ByVal instring As String)

 ' where instring is the name of an xlsx workbook
 
 Dim result As Integer
  
 Dim rootPath As String
    rootPath = ThisWorkbook.Path
    rootPath = rootPath & "\"
    'MsgBox "root path " & rootPath

  
 Dim Filename As Variant
 Filename = rootPath & "\" & instring & ".xlsx"
 If instring <> "" Then
    result = LRS_do_one(Filename)
 End If
  
 End Function

Function LRS_do_one(Filename)
  
 MsgBox "Doing " & Filename     ' gives popup w expected results
 
 Workbooks(Filename).Open       ' doesn't to anything
 Workbooks(Filename).Activate   ' doesn't to anything
 Workbooks(Filename).RefreshAll ' doesn't to anything
 Workbooks(Filename).Save       ' doesn't to anything
 Workbooks(Filename).Close      ' doesn't to anything
  
End Function