OK - I don't know what that workflow does, but I hope it works.
For anyone else reading this, my "guess" is that the predefined computer is not managed and therefore the task doesn't start. We've seen this on other systems where you schedule a task on a predefined computer and it's waiting for the predefined computer to boot into automation before it will start the task. Once in automation and reporting in to the console, the task "schedules" and runs.
That said, it's not the answer to the problem posted above per-se, but it may be useful information.