I have 2 4GB sticks of ram, but only one of them is being detected. I haven't installed my OS yet, but when I turn my computer on and the boot screen pops up (I have no idea what this is called, sorry), it says that only the RAM in the A2 slot is being detected. I have another in my B2 slot. I've unplugged and replugged my sticks and switched them up, and am still having the same problem. Since I can switch the sticks and just the one in the A2 slot is still being detected, I don't think either of the sticks are defective.
My computer boots up fine regardless if one or two sticks are in, but I would really like to get the RAM from both of them.
Motherboard - Asus Z87-PLUS ATX LGA1150 Motherboard
RAM - Kingston Predator Series 8GB (2 x 4GB) DDR3-2133 Memory
He said he had one in the A2 and B2 slots so they are dual channel. It defiantly sounds like a Mobo issue but try (as shanky suggested) putting them in the A1 and B1 slots (if CPU cooler clearance allows)