API connector running but cannot make it in the Workflow

Hi Folks,
I am using some external APIs to SMS, Firebase with success. However, in the last 2 days I am struggling to implement a POST to a credit card payment API.
The API connector is working smoothly, but I am not able to make it run as an action in the Workflow using the same data that is working in the connector.
The data comes from database and need to be formatted as a simple JSON string to be POSTed to the endpoint.
The error is HTTP 400 - Could’t parse json object.
All authorization Keys are ok, otherwise it would not work in the API connector.
Tentatives made so far without success :

  • Using dynamic fields in the action plugin step based on the body defined in the API connector
  • Using javascripttobubble to build the JSON
  • Tried to format the string with escape codes “”",\, etc…
    This is the structure of JSON to be sent :
    { “CustomerName”: “”,
    When using javascripttobubble plugin, the structure changes to :
    { } and everything is built by the javascript taking core of all quotas and escapes.
    Despite of it working in API connector, I suspect to have a wrongly formatted string, but not sure how to solve.
    Would appreciate any hint about what I am doing wrong.

I have the same issue . Anyone has any clue ?