Integration with external API

Hi I have a requirement to integrate with docusign for digital signing of legal documents. I am getting the 400 error while doing so. Can you please point out if I am missing here something. Please find my code below:
Please note, the first call i.e, local!login is successful
load(
local!authHeader:"X-DocuSign-Authentication",
local!credentials:{"Username":"<useremail>","Password":"<userPassword>","IntegratorKey":"<IntegratorKeyGenerated>"},
local!signers:{"email":"recepientMail","name":"<recepientName>","recipientId":1,"routingOrder":1},
local!documents:{"documentId":419616 ,"name":"Affinity Physician Statement Form","documentBase64":convertdocumenttobase64(419616)},
local!emailDetails:{"emailSubject":"TestEmail","emailBlurb":"ShowsHowTocreateEnvlope","recipients":{"signers":local!signers},"documents":local!documents,"status":"sent"},

local!login:a!httpQuery(
url:"https://demo.do...

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