Like I said, I would do some Googling, or even just call ASUS (assuming that's an ASUS board) The Z170 chipsets were barely able to work with M.2 ssd when they came out.
I was just googling a bit and saw what I remembered...a lot of BS to get it to work on those early chipsets.
It did get a lot easier with the z270 then the z370 chipsets. :/
I wish I could be more help. :(
/e Still looking but right away I found this...
Version 3703 2018/01/128.09 MBytes
Z170-A BIOS 3703
Fixed SAMSUNG M.2 device issue.
Fixed SanDisk M.2 device issue.
Fixed AMD RADEON SSD device issue.
Improved DRAM compatibility.
/e From your manual... there seems to be a setting for M.2 drives in the Advanced / Onboard Devices Configuration
https://i.imgur.com/Gp7wV7O.pngYeah ill look into it, I just deleted the partition that was on their, since my Windows rufus key picks the drive up