Mario Kart 7 (3ds) online does not work?

Recently tried to play Mario Kart with my friend online but somehow my account is not displayed as online. My Nintendo is connected to the Internet and I can access other features as well, but I can't get into multiplayer using the app or friend card. My friend said he can't see that I'm online. My Nintendo shows but that he is connected to the Internet and I can also go to websites and see that my friend is online but not play Mario Kart with him. Already tried with my phone to make a hotspot but there it is the same problem. Does anyone know?

In the friends settings of the 3ds you can set whether you want to share online status with friends or not

Thanks, that was shown to me. Still, the game does not work online, although my friend can now see that I'm online