If you own or have recently purchased Crucial NVMe SSD such as CT1000P1SSD8 (1TB M.2 NVMe SSD) or CT500P1SSD8 (500GB M.2 NVMe SSD), please be aware that these devices may no be recognized by ESXi after upgrading to the latest release. Thanks to Pete Lindley, (OCTO for End-User Computing), who reached out last week regarding the observation as well as a workaround for the problem. This was also quite timely as I recently purchased a Crucial M.2 NVMe SSD and would have also ran into this problem.
It turns out these Crucial devices were working fine while running on ESXi 6.5 Update 2 but was no longer recognized in latest release of ESXi 6.7 Update 2. It is unclear whether support for these SSDs were removed intentionally or unintentionally, but in either case, these devices are not officially on VMware's Hardware Compatibility List (HCL).
UPDATE (05/23/19) - After speaking with a few folks who took a closer look, the issue is due to the fact that we added support for NVMe 1.3 spec in latest ESXi 6.7 Update 2 release, but because these are "consumer" devices, they did not conform to the latest specification and hence the driver is unable to claim the device. This is another good reminder when using components not on VMware HCL, this is always a risk from a home lab perspective. In general, I know Samsung and Intel NVMe SSD usually works quite well without issues but always good to do some research. I think Engineering is looking to see if there are other workarounds for the future, but for now, you can use the workaround below.
The easy workaround that Pete found was to simply replace the NVMe driver from ESXi 6.7 Update 2 (1.2.2.27-1vmw.670.2.48.13006603) with one found in ESXi 6.5 Update 2 (1.2.1.34-1vmw.650.2.50.8294253). To so do, simply copy nvme.v00 to /bootbank from either an existing ESXi 6.5 Update 2 system or directly from the ISO. Please note, any future updates or patches to the ESXi host will most likely override the updated driver.