I kept on getting the same error code 20115. Then I just did what Bighead did. I got a backup of my Wii's NAND, decrypted them and put it in the Dolphin Emulator\Wii folder without replacing the SYSCONFIG file from Dolphin. Now it works perfectly! I guess the problem is we need NAND Dumps.
Windows 10 x64 , Asus Maximus VI Hero LGA 1150 Z87,
Intel Core i7 4770K OC @ 4.0ghz with Noctua NH-D14
EVGA GeForce GTX 780 Ti Classified, Corsair Vengeance Pro 16GB DDR3 1866MHz,
Samsung 840 EVO SSD 120GB, NZXT Phantom 410 (Gunmetal) ATX Mid Tower
Intel Core i7 4770K OC @ 4.0ghz with Noctua NH-D14
EVGA GeForce GTX 780 Ti Classified, Corsair Vengeance Pro 16GB DDR3 1866MHz,
Samsung 840 EVO SSD 120GB, NZXT Phantom 410 (Gunmetal) ATX Mid Tower