Question Memory not being detected/PC not booting

[check2forlatency]

Hey guys, I just replaced my motherboard with the assumption that it was the reason my PC wasn't booting when my RAM was in a certain configuration but now it's still not booting into BIOS (only the fans spin up) when all four slots are filled. While all four RAM sticks are in, the DRAM Debug LED also lights up. I tested all four slots with a single stick, when DIMMA1 and DIMMA2 were occupied, the PC booted but it said "Memory module in non-optimized slot" and when DIMMB1 and DIMMB2 were occupied it started normally. However, at all times, the BIOS only read a single stick of RAM, the one in slot DIMMB2. I also checked the CPU for bent pins are there were none. What's the problem here?

CPU: Ryzen 7 3700X
Mobo: MSI X470 Gaming Pro Max
RAM: 32GB (4x8) Corsair Vengeance RGB 3600MHz CL18
GPU: Zotac GTX 1070 Amp! Edition

 

[Lutfij]

You should be populating the rams in slots A2 and B2, per the information in your manual, page 6. Speaking of motherboard's, which BIOS version are you currently on? If you can work with a single stick of ram, on slot A2, see if you're able to POST and then get into BIOS to check on BIOS version and update BIOS manually from there if you've got updates pending.

 

[check2forlatency]

You should be populating the rams in slots A2 and B2, per the information in your manual, page 6. Speaking of motherboard's, which BIOS version are you currently on? If you can work with a single stick of ram, on slot A2, see if you're able to POST and then get into BIOS to check on BIOS version and update BIOS manually from there if you've got updates pending.

Sorry, I mislabeled them. I was placing the RAM in slots A1 and B1 when it read "Memory module in non-optimized slot" and A2 and B2 when it booted fine but only read 8GB in the BIOS. As I mentioned in the OP, this is the 2nd mobo I am trying. They are both updated to the most recent version from the MSI website as of 2020-04-28. The system POSTs and boots into Windows fine with a single stick of RAM in slot B2, but if I try occupying slot A1 and A2, those two sticks don't show up in the BIOS. If all four slots are occupied, the PC does not POST, only the fans spin.