Maybe you used Notepad+ Sam?

It is obvious that since Excel opens it ok, and a short test that I did, that your CSV files M are vbLF delimited. As such, one line of code needs to be changed. 
Sub M_snb3()  
  Dim sn() As String, c00() As String, j As Long, jj As Long
  Dim sp() As String, y As Double


  sn = Filter(Split(CreateObject("wscript.shell").exec _
    ("cmd /c Dir ""X:\snb\maxxino\table\*.csv"" /b /s").stdout.readall, vbCrLf), ".")
    
  ReDim c00(1 To UBound(sn) + 1, 1 To 2) As String
    
  With CreateObject("scripting.filesystemobject")
    For j = 0 To UBound(sn)
      y = 0
      sp = Split(.OpenTextFile(sn(j)).readall, vbLf)
       
      For jj = 0 To UBound(sp) - 1
        sp(jj) = Log(Split(sp(jj), ",")(5)) / Log(10)
        If jj > 0 Then y = y + 100 * (sp(jj) - sp(jj - 1)) ^ 2
      Next jj
      'c00(j + 1, 1) = sn(j)                'CSV Full Filename
      c00(j + 1, 1) = .GetBasename(sn(j)) 'CSV Base Filename
      c00(j + 1, 2) = y                    'Result
    Next j
  End With
    
  Range("A1").Resize(UBound(c00), 2).Value = c00
  Columns("A:B").AutoFit
End Sub
IF the decimal separator is an issue, you can change it from the hard coding in the code to use the regional setting by:
Application.DecimalSeparator