Nope
I think I didn't, but I just skimmed through the settings trying to change various things to see if it unlocks something, but to no avail.
Alright, try this:
Go to Profile (first option), under Other Settings.
Note what it says on the top screen (User Name, Birthday).
Then, click Nintendo DS Profile.
Note the name on the top and the birthday.
If the two don't match (the 3DS name/birthday and DS name/birthday), then that's the problem. To fix it:
Go back one screen to the regular Profile screen.
Change your Username by one letter (save it and everything), and then change it back to the original.
Then, do the same for the birthday (change it by one day or something, save it, then change it back).
Now, check the Nintendo DS profile, and the two should match.
After that, and when you verify that your connection is working and everything, try connecting in-game again.