Excel VBA - File created not opening suddenly

Hi. I use the following code to create separate file copies of some of my sheets. Opening the resulting copy files has worked well for over 5 years and now suddenly I am getting the error in the attached image. when Itry to open the files



Sub oSave_Individual_Numeric_Sheets_As_Files()

Dim oDate As String
Dim oHole As String
Dim oLevel As String
Dim oShaft As String
Dim oSheetName As String
Dim xPath As String
Dim xWs As Worksheet
Dim xWb As Workbook
Set xWb = Application.ThisWorkbook
Dim F As String
Dim FileExtStr As String
Dim FileFormatNum As Long

Application.ScreenUpdating = False
Application.DisplayAlerts = False

On Error GoTo EH

xPath = ActiveWorkbook.Path

    For Each xWs In ActiveWorkbook.Worksheets
        oSheetName = xWs.Name
        If IsNumeric(oSheetName) = True Then
   
            oDate = VBA.Format(xWs.Range("F7").Value, "yyyy MMM dd")
            oHole = xWs.Range("F8").Value
            oLevel = VBA.Mid(xWs.Range("F9").Value, 1, 2)
            oShaft = xWs.Range("J12")
            xWs.Copy
           
            '****Get the right file format for the version of Excel
            If Val(Application.Version) < 12 Then
                FileExtStr = ".xls": FileFormatNum = -4143
            Else
                Select Case xWb.FileFormat
                    Case 51:
                        FileExtStr = ".xlsx": FileFormatNum = 51
                    Case 52:
                        If Application.ActiveWorkbook.HasVBProject Then
                            FileExtStr = ".xlsm": FileFormatNum = 52
                        Else
                            FileExtStr = ".xlsx": FileFormatNum = 51
                        End If
                    Case 56:
                        FileExtStr = ".xls": FileFormatNum = 56
                    Case Else:
                        FileExtStr = ".xlsb": FileFormatNum = 50
                End Select
            End If
            'First save new workbook to shaft named folder
        F = xPath & "\Individual Holes\" & oDate & " " & oShaft & " " & oLevel & " " & oHole & FileExtStr

            ActiveWorkbook.SaveAs Filename:=F, FileFormat:=FileFormatNum
            ActiveWorkbook.Close False
           
        End If
       
   
    Next
   

   
    Application.DisplayAlerts = True

    Exit Sub

EH:
    MsgBox Err.Description & " eh55"
   
    Application.DisplayAlerts = True
   
End Sub