Audi navigation updates are released every 6 months and have a whole year and part year numbering scheme. If you have a 2018 car, depending on when it was built you could have a licence for any of these maps:
2017/2018
2018
2018/2019
2019
if you are licensed for 2018, anything before this date will work as its "up to" 2018. Anything newer would need you to purchase a licence to use the newer maps data.
When you are next in the vehicle, after turning on and allowing the media system to boot, select and hold NAV, and while still holing NAV select and hold MEDIA. After a few seconds the media systems update menu will display. navigate to activation keys. These are a list of your media system licences. All will show as 000XXXXX (where X = a number and or letter) bar one which will display as 0XXXXXXX. Post this digit string here and we can tell you what you are licensed to use.
Audi SD cards use a hidden partition with a CID (Card Identification Register) on them. So the system knows if you are using a genuine card or not. If the system has not be modified then a non Audi card will not work.