2014 XF economy mode

Hi folks, I recently traded my beloved 2003 S Type for a 2014 XF supercharged 3L V6 model. Love the car!
When I test drove it, the engine stopped at a red light, and restarted at a touch on the throttle. Now after two months driving, it does not. I have tried the button to engage and disengage the ECO system numerous times, but no change. I am still waiting for the dealer to get me an operating manual for the car, so I am a bit in the dark. Can anyone suggest a remedy?

Does the car have an auxiliary battery for the stop/start system? If so that might be one place to start looking.

Thanks for the tip Robin. As I say, I don’t have the manual yet, and I’ve only had the car a couple of months, but I will investigate.