You may have noticed that today the 3ds firmware has been updated to V7.0.0-13 and it has been confirmed this new 3ds firmware has blocked server flashcarts. this post will just tell you when you can update your 3ds to V7.0.0-13 or how to use a flashcart to work on this new 3ds firmware.
Before you update your 3ds to this new firmware. you need to check whether your card can work on the new firmware, i have tested some cards and confirm currently r4i gold 3ds card and r4i-sdhc 3ds rts card can work great on the new 3ds firmware without updating. so if you have any of them, feel free to update your 3ds and your flashcart will be working great on it. And if you want to buy a new flashcart for your 3ds V7.0.0-13, r4i gold 3ds is the best choice.
If you find your flashcart currently can not work on the 3ds V7.0.0-13, make sure do not update your 3ds for now, you need to wait until you see the official site of your flashcart release the udpate patch and then you update your flashcart to make it work on the 3ds V7.0.0-13, then update 3ds after you update your flashcart successfully. for example, supercard dstwo currently can not work on the latest 3ds firmware, dstwo users need to wait the official site can release the patch later and then update the dstwo card.
So Do Not Update Your 3DS/3DS XL Firmware Unless you confirm your flashcart can still work on your updated 3ds firmware.
Do yourself a favor, don't buy crappy flashcarts.