Well that was weird. I tried all sorts to get the smart keys to work, even the app stopped working. With first one key in the car, then the other, BT on and off. No errors on car scanner but cleared faults anyway. Nothing worked so I decided to try the battery disconnect, took both keys out to the car got in and it just turned on (laughing at me), never got as far as the battery. Now the app works again though not all items on it, e.g. I cannot start the AC or heating but it will now let me use keyless start.
Strangely it would always lock and unlock via the keys and phone but wouldn't turn on even with a key on the backup position.
Maybe it needed to see both keys to reset whatever?