Mattie
I too have recently purchased an A4 ( 1.4 Sport 2018) from an Approved Audi dealer, so have just been through the "setting up" processes. I had 2 sets of keys, one of which had a white/clear plastic tag approx 70mm long attached, the tag contained the key number and a silver "scratch off" label. When I scratched the label there was a 10 Alpha character code eg ABCDE FGHIJ . I used this code and was able to set up. Worth phoning up a local Audi dealer to see if can assist ?
Whilst on - a question for you, have you managed to "Display tyre pressures" ? I have set the tyre pressures, on a cold morning but according to the manual the car has to be moving to view the pressures, I can get to the "Tyre Pressure Loss" screen then the next message is Cannot view whilst moving. !!
Hope this helps
Trevor
