HOW TO SOLVE ONE RAM SLOT NOT WORKING PROBLEM

Which two RAM slots to populate on a 4-slot system? ram slot 3 and 4 not working 10M Followers, 3 Following, 307 Posts rama slot Hallo, also ich hab das Problem dass wenn ich meine Ram in Dual Channel sprich auf Slot A2 und B2 aufs Mainboard stecke geht der PC nicht an

ram slot 1 and 3 or 2 and 4 B550M DS3H ; 1 Solid Pin Power Connector ; 2 DVI ; 3 DisplayPort + HDMI ; 4 Realtek GbE LAN ; 5 Ultra Durable PCIe Slot · PCIe® Slot · Running 1*