Unable to Get StepResult Attachment list

I am trying to fetch all attachments of a StepResult (API Document Refrence) but when ever I am trying to call the API I am getting 
{ "errorType": "ERROR", "clientMessage": "We encountered some problems during processing this request. Please try again!", "errorCode": 104 }

above mentioned error. What is the problem is it in my end or some internal error.

Please let me know what is the issue 
I am attaching the api call page for refrence