Whenever an Internet friend and myself attempt to exchange friend codes [over the internet], I can add their code just fine, but my friends always say that my code keeps coming up as "invalid," despite the fact that I have memorized my code and know my code by heart.
Is something blocked on my 3DS that makes other 2/3DS's unable to add me? Am I supposed to change some kind of settings in my 3DS to make the code "valid"? Any help appreciated; thanks!