So my circle pad was acting up and I am wayyyy beyond my warrenty. (I have a launch 3ds)
I opened up my 3ds and cleaned out the circle pad, When I put it back together and loaded it up, thats when things got wierd. The date was 1/1/2011.
16 hours later, I still haven't streetpassed my sister's 3ds. I've tried deleting all streetpass data Via system settings and recreating it within each individual game and mii plaza. Still nothing. (its been about 6 hours since I did that)
I read that there was a bug like this a while ago but that it was supposed to be fixed since about a year ago.
Also I am not going to format my system memory. I have all streetpass hats and all puzzles complete up to the beginning of july. And a full friends list. I don't want to lose any of that.
Edit: Fixed the issue. Apparently all you have to do is this:
1. Delete all streetpass data via system settings.
2. Go into streetpass plaza and reenable streetpass.
3. Change your mii (or hat), then disable streetpass.
4. Reenable it then change it back to how it was before.
Then go and reenable streetpass in all your other games, you'll streetpass again in 8 hours.
OR streetpass someone you haven't streetpassed before and it will auto-fix.