Question New Computer Build Help Please

Apr 3, 2019
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I built a new computer with a Ryzen 5 2400G and an ASROCK B450M Steel Legend. The computer won't post unless there is only 1 stick of RAM and it has to be in the 4th slot. Both sticks work in the 4th slot so I'm assuming the problem isn't the RAM. I just RMA'd the motherboard as I just assumed that 3 slots were bad but the new replacement has the exact same issue. My next guess is that it's the CPU. Am I correct in this thinking or is it possible that it's the RAM?