WhatsApp Business API - WhatsApp Flow problem sendig payload to endpoint

I'm developing a Flask app to store data from my clients (Datakinder parents). I am receiving the request and decrypting the message successfully. But I always receive incorrect data On on-click-action' I expect to receive user typed data but I always receive ${form.parentname} , not the user data

Footer code is:

                        "type": "Footer",
                        "label": "Siguiente",
                        "on-click-action": {
                            "name": "data_exchange",
                            "payload" : {
                                "parentname":"${form.parentname}"
                            }
                        },
                        "enabled":true
                     }

At clicked "Siguiente" (next), endpoint receive data={'parentname': '${form.parentname}'} it must be : data={'parentname': 'Alejandro'}

Any Idea?

I sent fixed data in payload and it was received properly, but form data is not

I have a few questions to help debug the issue:

1. Can you check if the Footer component is inside the children list of the Form component?
2. Can you share a minimal flow JSON to reproduce the issue?
3. How are you testing? On a phone or Flows Builder?