Problem connecting to the router
With our 3DS, we were getting the error code 003-1099 (sounds like a tax form!), which is the error for when it cannot find the router or access point to connect to. While a search of the Internet turned up other suggestions (mostly to not be confused with configuring the DS settings, which are separate from the 3DS settings), our problem turned out to be much more basic – case sensitivity. Make sure your SSID matches exactly, case included.