Hi Gary, before loosing any data, I suggest, to boot from a liuvefile linux. Please use a modern livefile like Knoppix or Kali-Linux.
If it is not a BIOS problem, you should see the device again and are able to mount it. If /root is on a seperated partition, you can do some filesystem checks, like e2fsck or else. Ans: Most important, with a livefile system you can mount an external harddrive and backup all files. Thus , even when the /dev/nvme*** is died or partly broken, you can maybe restore /root on another partition. Second: Please check ACL, although I do not believe the reason for these, it is worth to look at this. Maybe you or someone else has chenged it accidently. Third idea: Is the harddrive full? In the past I has the problem, not to be able to do anything. The reason: My harddrive was completely full (some temporary file was the reason). Deleting this big file was the trick. Just some ideas, maybe it could help. Good luck! Best Hans
