I don't know if this still is the case but:
The old DS only supported WEP WiFi (no WPA).
Because of this homebrew and your DS only were able to use internet if you had a WEP connection.
I think this limitation might still be present in the DS Firmware for N3DS, but I haven't even bothered to check.
So, just if when you try it doesn't work, try setting up a WEP connection.
PS: But perhaps it works as it is, no idea.
PS2: I checked, you need a WEP connection because of that NDS limitation. Set up your router to use insercure shitty WEP for the WiFi if you really want to use this.