Only M.2_1 slot supports sata devices. Move your M.2 drive to M.2_1 slot.1 x M.2_1 socket 3, with M Key, type 2242/2260/2280/22110 storage devices support (both SATA & PCIE mode)*2
1 x M.2_2 socket 3, with M Key, type 2242/2260/2280 storage devices support (PCIE mode only)
Do you have the pro model of that mobo?I bought Asus WS x299 sage and installed Samsung 860 EVO SATA M.2 SSD 500GB, after power-up, UEFI BIOS Utility shows up but it doesn't show up my hard-drive.
Thanks for your suggestion, I tried to switch my M.2 drive on both ports, I also tried another M.2 SATA drive but it does not work.Only M.2_1 slot supports sata devices. Move your M.2 drive to M.2_1 slot.
M.2_2 can not be used for sata drive like 860 evo.
If M.2_1 is unavailable for some reason, then use M.2 to sata adapter.
NO Simple: "asus ws x299 sage"Do you have the pro model of that mobo?
The manual shows a LED beside the m.2 slot that lights when a sata ssd is installed.NO Simple: "asus ws x299 sage"