Error when opening nvidia-settings (ERROR: Unable to load info from any available system

I am using Centos 6.10 and having trouble with the nvidia-settings.
I was using MobaXterm to use TCAD Sentaurus Visual which requires GPU, and found that messages such as 'Xlib: extension “MIT-SHM” missing on display “localhost:10.0”. However, if I use XRDP, there is no such message appearing and the graphic works normally. I found out that the Nvidia driver is not installed, thus installed the nvidia driver (disabled Nouveau before the installation).

Now, I have both drivers not working and even in the XRDP program, the graphical work does not work, but error message ‘GLX driver is missing’ appears.

I tried to open nvidia-settings, but the it appears ‘ERROR: Unable to load info from any available system’

I am having hard time solving this problem and would really appreciate for help.
Thank you.

Below is my computer information:

uname -r


lspci | grep -i vga
03:00.0 VGA compatible controller: NVIDIA Corporation GP107GL [Quadro P620] (rev a1)
0a:00.0 VGA compatible controller: ASPEED Technology, Inc. ASPEED Graphics Family (rev 3)

if I type nvidia-smi, the output is like below:0)

Mon Feb 24 22:09:33 2020
| NVIDIA-SMI 440.59 Driver Version: 440.59 CUDA Version: 10.2 |
| GPU Name Persistence-M| Bus-Id Disp.A | Volatile Uncorr. ECC |
| Fan Temp Perf Pwr:Usage/Cap| Memory-Usage | GPU-Util Compute M. |
| 0 Quadro P620 Off | 00000000:03:00.0 Off | N/A |
| 26% 42C P0 N/A / N/A | 0MiB / 1999MiB | 0% Default |

| Processes: GPU Memory |
| GPU PID Type Process name Usage |
| No running processes found |
nvidia-bug-report.log.gz (1.09 MB)