Question Gigabyte X570 Gaming X Not Recognising Ram In Slots A2 Or B2

Dec 28, 2019
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Ive recently built a PC, my first build ever, ive got the gigabyte gaming x x570 mobo with Corsair Vengeance Ram DDR4- 8GBx2 Sticks @ 3200Mhz
Now when i put them in the recommended slots ( A2 &B2) The system would boot but not get anything come up on screen, so swapped them to the other 2 remaining slots(A1&B1) and they work fine, any idea as why this is happening?

thanks

Steven