How to add citaion in vectara, while testing its Multiple Corpora Query APIs?

How can I add citations in the response on Vectara? While testing the Multiple Corpora Query, I updated the citation in the payload. I followed the approach mentioned in the Vectara documentation. I have tried all the models mentioned in the documentation and followed the instructions on how to provide the citation style, but it is not showing citation in resposne.

"citations": {
  "style": "numeric",
  "url_pattern": "https://vectara.com/documents/{doc.id}",
  "text_pattern": "{doc.title}"
}

The documentation states that to use citations, one must specify one of the following summarizers in the generation_preset:

mockingbird-1.0-2024-07-16 (Vectara's Mockingbird LLM)
vectara-summary-ext-24-05-sml (gpt-3.5-turbo)
vectara-summary-ext-24-05-med-omni (gpt-4o)
vectara-summary-ext-24-05-med (gpt-4.0)
vectara-summary-ext-24-05-large (gpt-4.0-turbo)

I have used these models, but still, the citation is not showing in the response.