after_document possibly not working in client

[quakernbq]

Good Afternoon

We are trying to chain a document to sign after another one following these steps:

-Call to DocumentsCreateAsync to first document, and returns document info filled and OK.
-Call to DocumentsCreateAsync to second document, and returns document info filled and OK.
-Call this our method, filling signer AfterDocument:

//Sign document  method
  public Task<SignRequest.Model.SignRequest> SignDocuments(Document firstDocument, Document extraDocument, User from)
        {
            var signInstance = new SignrequestsApi();

            var signers = report.Signers
               .Where(s => s.ToWorkWith)
               .Select(s => this.PrepareSigner(s, s.Signatory, s.InPerson, s.Copy));

            signers.ToList().ForEach(s => s.AfterDocument = extraDocument.Uuid);

            var sign = new SignRequest.Model.SignRequest(
                who: SignRequest.Model.SignRequest.WhoEnum.Mo,
                fromEmail: from.Email,
                fromEmailName: from.DisplayName,
                document: firstDocument.Url,
                redirectUrl: null,
                signers: signers.OrderBy(s => s.Order).ToList()
            );

            return signInstance.SignrequestsCreateAsync(sign);
        }

Results:

-When signers sign the first document, the page redirects to sign request main webpage, instead to second document.

What we have tried:

-In the line "signers.ToList().ForEach(s => s.AfterDocument = extraDocument.Uuid);", we tried with .Uuid, .Url...and so on.

What have to be done to achieve a second document chained signature?.