Hello all, this problem occurs because the trigger body is not complete when you create the trigger via API call, the pipelineReference block lacks the field "type": "PipelineReferece". If you compare with the official documentation, you will see it there:
https://video2.skills-academy.com/en-us/rest/api/datafactory/triggers/create-or-update?view=rest-datafactory-2018-06-01&tabs=HTTP#triggers_create
Your body:
Documentation:
The UI will auto-fix the code to ensure consistency but the fixed code is not applied till the user Publish (deploy the changes internally).
To solve this problem, you only need to add that "type": "PipelineReferece" in your trigger body when creating the trigger via API, and you will be able to start it afterwards.