Issue with fetching report via API/SDK

I have a client who is calling the ReportService method of the SDK However, for a specific date, he is getting the below error: Code snippet as below: Console.WriteLine("Calling for Completed "); //between 14/3/2016 - 15/3/2016 report = eslClient.ReportService.DownloadCompletionReportAsCSV(DocumentPackageStatus.COMPLETED, Start,End); ERROR as below: Could not download the completion report in csv. Exception: The remote server returned an error: (500) Internal Server Error. HTTP GET on URI https://urldefense.proofpoint.com/v2/url?u=https-3A__esign.gecapital.com_api_reports_completion-3Fstatus-3DCOMPLETED-26from-3D2016-2D03-2D12T00-3A00-3A00Z-26to-3D2016-2D03-2D17T00-3A00-3A00Z&d=DQICAw&c=VYqX86BTGTb0qUlJR6u3o6qN7ETAZTsOJF32eVnCrok&r=ZC91TX_I64RoGE2_orv1jj_W_uRIgkFfpySQJ6i1An8&m=mjlVYXwB0fXWRYzu_Uyx6XOWpSybhr4yYNjhPMSzSXw&s=hoA_7qGOHKJ2cNUDfCyi5ExddNjynuYKlTQhdAe2qYk&e= . Optional details: {"code":500,"messageKey":"error.internal.default","technical":null,"packageId":null,"entity":null,"message":"Unexpected Error. Our technical staff have been notified and will look into the problem. We apologize for any inconvenience this may have caused you.","name":"Unhandled Server Error"} Can you please take a look and advise us what is incorrect?