My 3DS won't connect to the internet?

I have a 3DS and I had the same issue.

Go to system settings—> Internet (or equivalent) and make sure your SSID (password) matches the password of your wireless. If you do not know your password for your wireless (many people do not because you only need it for when something screws up) the first one will always be the 15 or so digit number at the back of your modem.

And if you have access to your routers settings turn off it asking for a password so you can confirm it at least works. A friend had a problem with a ATV2 where it wouldn’t connect. She turned off it asking for a password and it worked. From there we were able to narrow down the problem to WPA2. So from there a easy fix.

Was going to say the same as @sparrowfeed

Oh PS. Once you get the 3DS connected, you need to download a game called Colors 3D from Nintendo EShop.

Try setting up your 3DS with a static IP . .
Check how here—> http://www.nintendo.com/consumer/systems/3ds/en_na/ts_internet.jsp
click on Help with Wireless Routers
click on How to Perform a Manual Setup
click on Nintendo 3DS Connection Files
follow rest of the instructions . . .