Error 20100 means Dolphin couldn't connect to Nintendo WFC... Since you dumped the certificates and put them on the correct folder, make sure Dolphin isn't being blocked by your firewall. By the way, the error pauldacheez mentioned is 20115. Using the latest development builds should fix error 20115 (if you encounter it)
Avell A70 MOB: Core i7-11800H, GeForce RTX 3060, 16 GB DDR4-3200, Windows 11 (Insider Preview)
ASRock Z97M OC Formula: Pentium G3258, GeForce GT 440, 16 GB DDR3-1600, Windows 10 (22H2)
ASRock Z97M OC Formula: Pentium G3258, GeForce GT 440, 16 GB DDR3-1600, Windows 10 (22H2)