https://www.youtube.com/watch?v=dp638J28epQ
The recent DSi firmware slipped in anti-piracy measures that made it impossible to run R4-style carts. Days later, the firmware already appears to be cracked.
https://lastchance.cc/nintendo-slips-in-anti-piracy-measures-into-dsi-update-5327010%3C/a%3E%3C/p%3E
Thanks, JY!