NVIDIA-SMI has failed because it couldn't communicate with the NVIDIA driver. 
Make sure that the latest NVIDIA driver is installed and running.

Situation:
Cuda: did install NVCC-V: messages appear

Solution:
1) query the current NVIDIA driver version number

ls /usr/src | grep nvidia

#if output: nvidia-450.57

2) Install relevant tools

sudo apt install dkms

3) Reinstall the driver

sudo dkms install -m nvidia -v 450.57