If your firmware string says HN+_US_AU3G... but you are currently in Europe or another region, you cannot simply download an EU firmware update. Attempting to do so will cause region lockouts. You will first need to convert the region ("europize") your system using specialized diagnostic tools like VCDS or OBD11, or consult a professional tuner. 3. Preparing the SD Card for the Update
What is the you are currently seeing on your screen? audi mmi 3g plus firmware update link