If running a DS game didn't work, try using one that specifically HAS to load the username; Plants vs Zombies is a good example (it shows your name right on the title screen). If that still doesn't work, then try loading System Settings on an up to date emuNAND (or 9.5 if you have a N3DS), access DS Profile settings, and then go back into sysNAND and try again. If that doesn't work, then I don't know what will other than completely reinstalling System Settings on sysNAND.