"The save data could not be acessed - Please turn power off and insert DS Card!"

Hi
Sorry if something like this has been posted before!! - this is the message I'm getting with all Ben 10 games - could someone help please?
Many thanks
Gen

We need to know what you are using to play the game. Emulator, flashcart on a ds, etc.

Read this.
https://www.romulation.org/forum/index.php?topic=1462.0