Mike, Sorry to hear that, Stop-Start is a complex function and perhaps someone with more experience of VAG units can comment on. My Yeti does not have it by my missus' Mini will not stop-start if:- temp below ~+4C
- coolant temperature not up to nominal
- battery voltage is below or drops below nominal
- you have just used reverse
- the bake servo pressure has dropped
- you have deselected it!
One of these may be causing your loss of stop-start a good run should get battery back to nominal unless the battery has a failed cell. Voltage check would be a worthwhile check to make sure. Good luck