B550 Steel Legend with NVME + Sata III

Hi everyone,

I'm happy with my PC since january with a NVME SSD drive (ADATA SX8200PNP) in the M2_1 slot.
I'd like to increase the sotrage, so I've adda WD Blue 2To Sata III drive (WDS200T2B0B) that I've set on the M2_2 slot of the MB, but it's not recognized, neither in windows nor in the bios.

This WD Blue SSD is part of the compatible drive list provided by Asrock : https://www.asrock.com/MB/AMD/B550%20Steel%20Legend/index.fr.asp#Storage
WD     2TB     SATA3     2280     WDS200T2B0B-00YS70

I use no sata plug, so the M2_2 lane should be free.
i've updated bios (V1.90) and chipset.

Others components :
-AMD Ryzen 7 3700X
-GeForce RTX 3070

Any idea of what's going wrong ?

According to the manual for your motherboard, the second M2 socket shares SATA3 5 & 6. If the SATA3 ports are configured for use, the M2_2 socket is unavailable. There is likely something in the BIOS that configures the motherboard such that SATA3 5 & 6 are disabled so that M2_2 is enabled. In essence, it reads like your motherboard is configured to use the SATA cabled ports rather than the M2 socket. You'll need to poke around in the BIOS to set it correctly.

There must be a place in BIOS where the SATA ports 5 & 6 are set to active, or a place to activate the M.2 slot. Ut might be something like the SATA ports showing as AHCI. It's not likely that BIOS would automatically deactivate the SATA port 5 & 6 if an M.2 drive is detected. Once you find that setting, the M.2 should come to life.