[SOLVED] Second m2-slot does not work

[South Jansen]

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 something Else. I dont know alot about This so i would really appreciate some help.
(Sorry for the bad English)

 

[Barty1884]

Assuming B360M-Plus Gaming S?

1 x M.2 Socket 3, with M key, type 2242/2260/2280 storage devices support (SATA & PCIE 3.0 x 4 mode)
1 x M.2 Socket 3, with M key, type 2242/2260/2280 storage devices support (PCIE 3.0 x 4 mode)

https://www.asus.com/us/Motherboards/TUF-B360M-PLUS-GAMING-S/specifications/

What M.2's are you using, specifically? Only one slot supports SATA drives.