It has to be a map card not a standard SD card. It reads the CID off the card. All Vag map cards are interchangeable the unit knows it's a Vag card so allows. Not a VAG mapcard, it wont work for navigation with standard firmware. Some people get their units hacked but just as good to use VAG cards.The v8 is an original card. I've backed it up. Im using a different sd card, not rewiting the original. I've copied the new unzipped maps and copied overall.nds file from the v8 backup to the new card.
If you have two Vag maps cards and experimenting that's where you need to put the long hold in on the on/off to cause a reboot else it misread what you put in.