Agent not triggering on state change via JSON

Summary:

We have a use case where we receive a state change via a confirmation/ack through REST API with the following configuration:

The status 'MER.MEDICION_ENVIADO' changes correctly in the shipment but, we have an active agent with an Agent Event of 'SHIPMENT - STATUS CHANGED' and with the following configuration (first and second image) that is not triggered to change an ATTRIBUTE11 (third image) that we have to indicate the status colour to the business area, like an indicator.

The indicator should change from white to green upon receipt of the JSON and the agent trigger (as it does work correctly using XML), but it does not fire with REST API.