When trying to retrieve license keys from Plesk panel, are you getting an error :

Licensing Server Unreachable: Unable to connect with licensing server.
Please make sure that your network allows communication to ka.parallels.com:5224.

Login to your server via SSH and check if connections are getting through to the Plesk license server :

# telnet ka.parallels.com 5224

If it is not getting connected, allow the IP ‘’ in the server firewall.

# csf -a
Adding to csf.allow and iptables ACCEPT...

# telnet ka.parallels.com 5224
Connected to ka.parallels.com.
Escape character is '^]'.
Connection closed by foreign host.

Once this is done, you can try retrieving the license keys from Plesk.