This might also be due to differences in microSD cards. For some weird reason the N2DS XL seems to have more stable connection than N3DS when connected to DSi.The DSi and 3DS do not have to have Wifi enabled in their respective system settings to be able to connect.Try to start with one of the confirmed working games from the list. At the moment you will most likely have to try to connect several times in a game before you manage to establish a connection.N3DS-N2DSXL using any combination of builds.DS-3DS using unknown build(s) through Twilightmenu++.These combinations have been tested and found to work: For linking to work, the combination of systems seem to be significant.For the DS you will need to enter WFC settings in a WFC compatible game.For the DSi and 3DS you can find it under internet settings in system settings.
You will have to enabled this every time you start GBARunner2. This is to make the dummy MAC addresses appear in the gbarunner2.ini.