error in file service upload via API

hey,

i’m trying to upload a file via API call with this endpoint - 

https://yul1.qualtrics.com/API/v3/automations/{automationId}/files

the file is in CSV format, im using multi-part payload and the CSV file data is also inside the body payload, im getting 400 error code with this error message:
 

{"meta":{"requestId":"*********","httpStatus":"400 - Bad Request","error":{"errorMessage":"Unexpected end of input"}}}

anyone can help to understand that error code? what i did wrong?

thanks!