As we know that yesterday nintendo official has released the new 3ds firmware V4.5.0-10, the new 3ds firmware blocked flashcarts. check the post here: Warning: 3DS New Firmware V4.5.0-10 Released, blocking flashcarts again! today supercard dstwo official site has released the new firmware V1.19 for working on the new 3ds firmware. If you already have bought the supercard dstwo card, just use the new firmware to update your dstwo card, your supercard dstwo will be working on the updated 3ds. Currently supercard dstwo is the word's first flash cart that work on the 3ds new firmware. and r4i gold 3ds card is also working on the 3ds new firmware, but just for the new card. about other cards, you still need to wait until the official site release the update patch later.
Download: dstwo new firmware V1.19 for 3DS V4.5.0-10
Here is the update guide: How to update your supercard DStwo to work on 3DS V4.5.0-10 with firmware V1.19
Do yourself a favor, don't buy crappy flashcarts.