C# SDK version 3.x.x Error: "OAUTH_SCOPE_MISMATCH"

C# SDK version 3.x.x Error: "OAUTH_SCOPE_MISMATCH"

When ever i am executing below method:

RecordOperations recordOperations = new RecordOperations();
                ParameterMap paramInstance = new ParameterMap();
                paramInstance.Add(SearchRecordsParam.EMAIL, Email);
APIResponse<ResponseHandler> response = recordOperations.SearchRecords("Leads", paramInstance);


I am getting below error

{{
  "code": "OAUTH_SCOPE_MISMATCH",
  "status": "error",
  "message": "invalid oauth scope to access this URL"
}}

I created account with scope ZohoCRM.Modules.all. My account is production  environment account. Someone from Zoho told me that to use C#SDK version 3.x.x you must have Sandbox environmnet account.
Please suggest the solution.