R4i Gold works with 3DS V7.1.0-14
I don't have a 3ds so not sure what the latest fw is. but if you are above that, or ever install fw after that for newer games, then your cart will be no good until theres a fw fix.
you'll need to install the latest woods fw onto your sd card for this cart.
I can get one for you at £10 if you are stuck finding 1, you will source your own roms, so make sure you know what you are doing.