Unable to fill customfields sending envelope

Hello, 

We are unable to fill the customfields of a template when we try to send an envelope on Docusign API REST.

The endpoint we are using is: {{baseUrl}}/{{apiVersion}}/accounts/{{accountId}}/envelopes

The body is the following: 

{

  "templateId": "xxxxxxxx-4240-4951-bdb1-f43315509f6e",

  "templateRoles": [

    {

      "roleName": "Signer",

      "name": "Test Name",

      "email": "test@test.com",

      "tabs": {

        "textTabs": [

          {

            "tabLabel": "Custom1",

            "name": "Custom1",

            "value": "Esto es el custom 1",

            "documentId": "1",

            "pageNumber": "1"

          }

        ]

      }

    }

  ],

  "status": "sent"

}

We previously created the field with the label Custom1. But when we receive the template result on the mail tray the fields values are not appearing. The collaboration checkbox is also marked. Any solution? 

Thanks in advance