Document not being passed to docusign

Hi, I have a requirement to integrate with DOCUSIGN where I am passing an appian document to be signed digitally. I used the httppost() function to call the service. Here I need to pass the document in the body in base64 format. I have used convertdocumenttobase64() function to convert the document. The method is being called successfully but I am getting the below error :
{
"errorCode": "UNABLE_TO_LOAD_DOCUMENT",
"message": "Unable to load the document. Unable to load Document(1;a.txt.txt). Error: the document is corrupt, rebuilding failed"
}

Can please anyone help me to resolve this?

OriginalPostID-255248