I installed the driver successfully before. After a period of time, NVIDIA SMI found that the problem was still that one. Some blogs explained that the driver couldn’t work properly because of the kernel update of Ubuntu. The following method is effective without reloading NVIDIA driver.

check drive

 nvcc -V 

If the driver exists, the next step will be taken.
2.

sudo apt-get install dkms
sudo dkms install -m nvidia -v 418.56

418.56 is the version number of NVIDIA. When you don’t know, you can see the NVIDIA folder in the / usr / SRC directory, and the suffix is the version number.

After success, NVIDIA SMI finds that the driver of the graphics card is normal.

Reference: unable to connect NVIDIA driver: nvidia-smi has failed because it could’t communicate with the NVIDIA driver