I have prepared an instrument list in a csv file, which my API program then reads. My list is a combination of sedols, cusips and isins. I can see that the process successfully reads the sedols and cusips, but not the isins. I then get an error message: "An unhandled exception of type 'ThomsonReuters.Dss.Api.ValidationException' occurred in mscordlib.dll. Additional information: Instrument identifiers cannot contain null values. Parameter name: instrumentIdentifier"