Triggering customer notification of fulfillment via API - not working

Technical Q&A
1

Since updating my API to 2023-04, my customers are no longer being notified by email that their orders have been fulfilled. The fulfillment trigger works fine with my code below, but according to a support agent I spoke to, the notification trigger is missing. I’ve followed the API instructions precisely so I don’t see where the issue is.

{
  "fulfillment": {
    "line_items_by_fulfillment_order": [
      {
        "fulfillment_order_id": 1234567890
      }
    ],
    "tracking_info": {
      "number": "123ABC",
      "url": "https://some.courier/123ABC"
    }
  },
  "notify_customer": true
}