I've had trouble with Scheduled Departure (charging would start immediately) and the answer was to try different settings in the off peak charging section.
My electrical rate is the same 24x7 so I didn't think I needed to check or change anything in the off peak charging section. I think it's a bug in the car's firmware. So while your problem is slightly different than the one I saw I'd recommend you try different time settings for off peak charging. I changed the time when off peak would start and then Scheduled Departure worked. Then I changed them back and it still worked. That's why I think it's a bug in the car's firmware.
Here's a link to the post I made about the subject:
scheduled departure @100% or not?