We have a workstation with a W2600CR2 board, dual E5-2687W v2 Xeons, and a new NVMe PCIe X4 SSD (non-Intel). The SSD has booted successfully in other systems, but I cannot get it to be a bootable device on the W2600CR2, even after updating the BIOS of the board, and trying all possible BIOS options. After installing Windows on it, the EFI shell sees the drive as blk, but no fs.
As no NVMe PCIe SSD is found on the tested hardware lists (click http://www.intel.com/support/motherboards/server/sb/CS-033391.htm here for them) and because you ensured your system BIOS/firmware (as a whole) is at the https://downloadcenter.intel.com/download/24614/Intel-Server-Board-S2600IP-and-Intel-Workstation-Boa... latest, indeed, we, then, suggest the following:
1. Test the SSD on the different PCIe* slots.
2. If the situation still persists, please, check with the NVMe PCIe X4 SSD manufacturer to see if they officially validated it on the Intel® Workstation Board W2600CR2, and if so, what suggestions they have on their own, based on their own tests.