For future info, where the vehicle is fitted with an Auxiliary Battery, this feeds the electronics whilst the vehicle is operating in start / stop mode, maintaining a constant 12V supply to the sensitive electronics. If you find, over time, that the start / stop function fails to operate, it can be due to either battery beginning to fail. The main battery obviously provides the capacity to physically crank start the vehicle, whilst the Auxiliary battery provides the stable voltage.
Too many restarts in a short space of time, as in crawling traffic, will drop the main battery to the point where it automatically switches off the stop / start functionality until such time as the main battery has recharged itself with engine running.
Typically a main battery in a stop / start vehicle will be of the AGM style, and 5-years should be considered as the typical lifespan of the battery before replacement becomes a need.
N6 JMX