Reviews emphasize using a Class 10 SD card (max 32GB, formatted to FAT32). Cheap cards are the #1 cause of update freezes.
Updating the firmware requires high-quality media and stable power to prevent system failure during the 30–60 minute process. Audi MMI 3G Plus & 3G High 6.30.1 Maps update instructions audi mmi 3g plus firmware update download
Now that your MMI 3G Plus is on firmware 6.xx, you can: Reviews emphasize using a Class 10 SD card