I have a 5008GT and use CTEK StartStop charger. I find that I often need to do overnight charge on 2 successive days for S/S to get working again. It may take 15-30 mins driving before the car reactivates the S/S. If I remember to do an overnight charge every 4 weeks or so, I do not seem to run in to any problems with S/S. A regular overnight charge with the CTEK StartStop may be good for battery health and prolong its life.Same problems here with my 2020 3008 - after approx 18mths start/stop stopped. Dealer had car for 2 days! after which s/s/ worked for about a week. I don't really do long distance driving so I bought CTEK CS5 StartStop. After all night charging CS5 shows 'care' but s/s still doesn't work. Complained to CTEK who replied CS5 must be connected red to battery and black to chassis because of BMS (battery management system). My CS5 is connected red to battery and black to ground connector on firewall right of battery. Still no success.
I had 2 Audis Q5 & Q7 previously same driving habits s/s worked every time - never failed to work.
Now have a New 3008 Hybrid on order for hopeful delivery in July 2021 (?) I'm wondering if they'll have s/s fixed.