If you attempt to assign a job to a predefined computer (which, by definition, is one that has not yet checked in), it will assign, and immediately result in a failure. A drill-down into the job will show the following message:
"Unable to run the task on a legacy computer while the Legacy Agent Communication mode is turned off."
The resolution is to simple enable communication with legacy clients by going to Settings | All Settings \ Notification Server \ Notification Server Settings, and then turning on Legacy Client Communication. You will then be able to schedule the task.
Development is aware of this issue and researching a fix for it.