The file is not in use elsewhere, and is not password protected. Which user is supposed to be set up with write permissions to the file from FME Server?
FME Server Error message: "Excel Writer: Failed to save changes to the spreadsheet '\\\\data01\\pathname\\TermUtility\\LOCID_Output.xlsx'. Check that you have write permission to the file, it has no password protection and is not opened by another application. Error message is 'Permission denied.'"