Peugeot 2008 the stop start does not work.

The original fault was the orange warning light kept coming on. After a technical update remotely carried out that fault disappeared. Hoever from then on the Stop Start failed to work. Took my car to Peugeot Dealership where I was informed that it was likely to be the battery. Tests could be carried out but I would have to pay for some of those tests and a new battery if a fault was found with the battery. The car is under its 3 year warranty! I informed Peugeot that my car did not have this fault until the update was done. Peugeot would not change its position even when I stated that the car started on every occasion even during the winter months. I am a low milage driver but feel that this should not affect my car this way!
My daughter is also a low milage driver and has no Stop/Start problem with her car but it is not a Peugeot!