Welcome to INTEL forum. This could probably a connection or VPN prob. My suggestion would be:
1) After VPN connection is established, setup license path in Quartus II>>tools>>license setup.
2) Verify license server is running by using “lmutil lmstat –a –c <port>@<server> in BOTH server and client machine.
3) Ping license server via VPN or telnet <host>< port> to check the TCP connection is established
Please stop and restart the server. You need to allow the firewall access to the port number from both server and client machine.
You can also refer to link below for more detailed instructions for Setting up a floating network license server (page 37 of 59):
You can also refer this following YouTube for license setup. https://www.youtube.com/watch?v=Ob9ei5lMgG
You can also refer to this following YouTube on Setting up and debugging Quartus floating licenses.
Let me know if this information is helpful