Problem: Can't add new recipient after Envelope creation (UNSPECIFIED_ERROR)

Hi all,

I’m trying to add a new recipient to an existing envelope after it has already been created.
I’m using the following endpoint:

/restapi/v2.1/accounts/{accountId}/envelopes/{envelopeId}?advanced_update=true&resend_envelope=true

(from the Docusign Documentation)
It works fine for all recipients, except for the one I’m trying to add after the envelope was created.
When I try with this new recipient, I get this error response:
"UNSPECIFIED_ERROR"
Object reference is not set to an instance of an object
 

I’ve tried multiple approaches and endpoints, but none of them worked.
Here’s one of the request bodies I’ve used:

{
  "recipients": {
    "signers": [],
    "agents": [],
    "editors": [],
    "intermediaries": [],
    "carbonCopies": [],
    "certifiedDeliveries": [],
    "inPersonSigners": [],
    "seals": [],
    "witnesses": [
      {
        "witnessFor": "1",
        "name": "teste",
        "email": "nahh336@gmail.com",
        "recipientId": "3",
        "routingOrder": "3",
        "recipientType": "witness"
      }
    ],
    "notaries": []
  }
}

I’ve also tried sending only the witnesses object without the recipients wrapper, but it still fails.
 

From what I understood, when the envelope is created, DocuSign defines a currentRoutingOrder.
If at creation time there are only 2 recipients, the currentRoutingOrder will only consider those two.

When I later try to add a third recipient, the envelope doesn’t update the currentRoutingOrder to 3 — it keeps going back to 1 (the first signer’s order).
Because of that, the envelope status stays as “sent”, and I can’t update or resend it to the newly added recipient.

Does anyone know how to fix this without having to clone or recreate the envelope?
I just want to add a new recipient to an existing envelope.