99 of the time this error means that the network that you are connecting to is secured using wpa encryption. Nintendo ds game cards are only compatible with wep security and are not compatible with wpa security.
Ds 6 5 Gt Administration Guide
The access point s security settings are not supported ds. Tap test connection at the top of the list of entries here to determine if your ds is able to make a connection. For nintendo 3ds on the 3ds a gamefaqs message board topic titled access points security settings arent supported by the ds. Click the big blue button connection settings and use that not the nintendo ds connections button below that. If you change the networks security type you may also need to change this setting on wireless devices that connect to the network such as any pcs or smart devices. Access your routers settings page and update the network wireless security settings to use a supported security type. Error code 51300 or 51099.
Once you know the wep key you will need to enter it when prompted. If you do have wep security you will need to enter a wep key on your nintendo ds to use the access point. So while you can enjoy other online features of the nintendo dsi and nintendo 3ds with wpa. The padlock icon next to the ssid name will be locked and a gray color. The wep key is usually found in the security tab of your wireless router settings. For pokemon platinum version on the ds a gamefaqs message board topic titled the access points security settings are not supported by the nintendo ds.
Scroll back up to step 3 of this page for the step by step. This means the security code entered into the nintendo dsi is not the same one the router is set to. In some cases this may be all the manual information required. You need to enter system settings and choose the top left icon internet settings.
Gallery of The Access Point S Security Settings Are Not Supported Ds
