It is only possible to update the maps for the first 60 days after first use.

Suggestion:
1) Always back up the SD card before it is activated (Simple copy of contents)
2) Do not use the card in MB download Manager until it is known that an update exists
3) When a map update is available, reset the backup to the card and then activate it again in the car and try to update maps in MB Download Manager.

MB Download Manager will "think" that we have just activated the card and still have 60 days of free updates and we can at least be entitled to a free update.

At this moment what is really lacking is sharing the contents of the SD card and info of the respective CID and SD Label