Hi,
I've noticed my problem for a few weeks now.
Before that, there were like 3-4 months where I didn't use my 3DS at all, I don't know if that is an important detail.
Anyway, I've been having some problems with Mii Plaza not adding people anymore. I know I've met many people, as I got notifications of new people in my games as well as the usual green light appearing on my 3DS.
I saw somewhere that I had to remove the Mii Plaza data from the Preferences, hence turning Mii Plaza off for Streetpass, and then go in Mii Plaza itself and turn it back on. When I do that, it starts adding people again, but only until I shut down the 3DS when I'm done for the day. The same bug starts again the next day.
So I wonder what I have to do to make Mii Plaza works again, all the time with no bug,. Anyone knows??
For your information, I own a 3DS XL (grey, the one that came along with Mario & Luigi Dream Star), and currently have about 1650 different people in Mii Plaza, more than 2000 encounters.
Thanks!