Try again with the code
Private Sub Workbook_Open()
Dim i As Long
For i = 2 To ThisWorkbook.Worksheets.Count
Worksheets(i).Visible = xlSheetHidden
Next i
End Sub
'This is workbook event code.
'To input this code, right click on the Excel icon on the worksheet
'(or next to the File menu if you maximise your workbooks),
'select View Code from the menu, and paste the code