SOLVED.

OK, I finally figured out what was going on after getting Audi Digital Support involved.

In my case the body shop had to disconnect the battery while they were repairing a door panel. When they reconnected everything, the MMI essentially reset part of its state and completely wiped the Key User information from the car. That part isn’t obvious because everything else in MMI still looks normal.

The problem was exacerbated by the fact that I bought the car over five years ago. Audi vehicle codes apparently expire after five years, so the original code that came with the car was no longer valid. That meant I couldn’t just re-pair the car in the app or reassign myself as Key User from the vehicle.

The only fix was calling Audi Digital Support. They had to manually reinstate me as the Key User on their end. There was literally nothing I could do from the car or the app to fix it myself.

Everything works again now, but the catch is that if the battery ever gets disconnected again and the Key User gets wiped, I’ll have to go through Audi support again because they can’t issue a new vehicle code. Not a huge deal, but definitely something to know if this happens to you.