I had an issue with this through multiple software updates...took it in to service and they said nothing was wrong and it was at least partially working when I got the car back. I am suspecting them doing a full service mode reboot of the system fixed it... Had an intermittent A/C issue as well that they can't see anything wrong and I can't replicate.
You could try pulling the disconnect under the back seat and see if that fixes it...that is what I will do if it stops working again to try. Unfortunately it is getting cooler so I am running out of opportunities to test the functionality.