Hi JohnP007 - welcome to the illogical land of the SRX - the bottom line is that the rear climate control just can't be set to stay on, it needs to be turned on every time it's needed. This is brought to you by the same crew that came up with the CUE and the triple horn honk that can't be defeated. What do you expect for > $40K...........
When you set the rear zone climate settings, they should stay set unless you "SYNC" from the front controls. If you SYNC then all the zones are controlled via the driver zone settings. Sounds like SYNC may be getting pressed after the rear zone has been set. I don't own a 2013 with CUE so I can't say for sure.
The settings (temperature) may be retained but the power button for the rear seat (on the back of the console) needs to be used to turn on the rear AC/heat every time that the SRX is started. At least that's the way that it works on my 2014 Premium edition. As I said before, welcome to SRX-land where function and logic have left the building............
The rear climate control must be turned on each time the SRX is restarted as stated by Marty E. That can be done by the power button on the rear control panel or the front touch screen in the Rear Climate Control section. I have two Climate Control icons stored along the top row so I can turn on the Rear Climate Control by pressing two buttons from the front seats.