m2 motherboard

Hey, I just got a Asus Tuf B360M-pluss motherboard. I bought a m2 disk with it. After a while i was in need for more space, and i found another m2 disk in my room, so i decided to put it in and because i knew it had Two m2 slots. But it wont show in bios or Windows. Its like the 2nd slot is for...