This most likely is just a mechanical problem with the shifter gate.
Take off the cover around the shifter gate. Around the second gear position, only visible from below the shifter, there should be a hex screw holding some kind of bracket. When this bracket has moved away from its intended position, the gear lever cannot move properly, blocking you from selecting some or all gears. You need to readjust the bracket and retighten the screw.
What does the transmission gear indicator in the dashboard say? In case all segments are lit instead of just the one currently indicating the selected gear, the transmission`s electronics have defaulted to "limp mode". If that is the case, I would pull the fault codes and check the ATF level. For the fault codes, please see
the manual available at the SJM auto technik site .
In order to check the fluid level, beware that this has to be done when engine and transmission are warm, plus you´ll most likely need to get a dipstick at an Audi dealer as most V8s don`t have one.
