Thank you for answers.
I turned off firewall and now I can see floating license is working. However, my PC is Windows 10 and my original license is for CentOS 8 so it seems running solver through my PC is not possible.
About the graphic issue, I'm using most recent version of the graphic card driver. So I tried to change display driver but it keeps showing message "The setting will be applied only when DEVICE is restarted". I thought I have to reboot the server computer but it didn't work. so I guess "DEVICE" is something else. How can I restart DEVICE?