VB.NET EXCEL - how to fix error The RPC server is unavailable

Replace :     
                    SaveExcel()
                    oExcel = CreateObject("Excel.Application")
                    oExcel.Workbooks.Open(FileLocation & FileName)
                    oBook = oExcel.ActiveWorkbook
                    oSheet.Range("A1").Value = "TEST"
With:
                    SaveExcel()
                    oExcel = CreateObject("Excel.Application")
                    oExcel.Workbooks.Open(FileLocation & FileName)
                    oBook = oExcel.ActiveWorkbook
                    oSheet = oExcel.Worksheets(1)
                    oSheet.Range("A1").Value = "TEST"