hi,
in one of my rigs suddenly disappear all cards 
i run nvidia-smi - i got “NVIDIA-SMI has failed because it couldn’t communicate with the NVIDIA driver. Ma
ke sure that the latest NVIDIA driver is installed and running.”
i run nvidia-driver-update but got the same
could you please help me?
I’ll try to assume that you tried to install new drivers and the installation was not completed correctly. You must complete the installation or reinstall the driver for proper operation.
i treed now several time command nvidia-driver-update and yes i got line in the end ERROR: Installation has failed
there is log
“ERROR: Unable to load the ‘nvidia-drm’ kernel module.
ERROR: Installation has failed. Please see the file '/var/log/nvidia-installer.”
Try this solution
https://devtalk.nvidia.com/default/topic/1031913/linux/driver-390-42-installation-failed-unable-to-load-the-nvidia-drm-/post/5252360/#5252360
fresh copy of hiveos helped - it was fastest solution