HELP M.2 SSD DOESNT DETECTED

[Pavendaxx]

I just purchase my m.2 ssd (WD Green 240Gb) today and install it on my pc, when i open the bios there is no m.2 hard drive detected there is just a generic massive storage device which is very very strange. So i decided to move the ssd to the second slot and it worked, but now my main hard drive is detected as generic massive storage. I dont know how this happened is theres some bios settings i should change or what. Because that problem i put my main hard drive on my hdd docking and it doesnt work, after the windows logo show it just bluescreened the error code is INACESSIBLE BOOT DEVICE. 

Let me clear things up, so there is two m.2 slot on my mobo (AORUS B450 ELITE) first i install my m.2 on the second slot which is at the bottom. The result is it doesnt detect the m.2 drive, the m.2 drive detected as mass storage device

second i try to move the m.2 ssd from the bottom slot to the slot located at the top under the cooler, that worked but my main hard drive doesnt detected, on the bios it says massive storage device.

Can you figure out whats the problem here? Because I want to clone my main hard drive to my new m.2 ssd. So both drive need to be detected at the same time.

[AndreiArgeanu]

When you install and SSD in either m.2 slot 2 of the 6 sata ports are disabled. You can see this in the manual of the motherboard and it tells you which sata ports are disabled depending on which M.2 socket is populated. I've also attached a diagram of the motherboard so you can see which sata ports is which. The reason to why your hard drive is not detected is because it's probably plugged in to one of the disabled sata ports.

[CPL_Jimmy]

Where is the other HD connected?  The B450, like many chipsets, shares lanes between the 2nd m.2 and SATA controllers.
Your mobo manual should have a handy chart that shows you which m.2 and SATA connectors you can use together.
The top m.2 should be the one run directly from the CPU and not the chipset.  

**Andrei explained it way better