Many times this error can be fixed by restarting the Plesk panel:
Make sure your openssl and curl packages are up to date:
// Centos / RHEL yum update openssl curl // Debian / Ubuntu apt-get update openssl curl
You can run the following command to see if your server can connect to the licensing server. You should get a response of Verify return code: 0 (ok) if the connection was successful.
openssl s_client -connect www.danami.com:443
If you get the error:
openssl s_client -connect www.danami.com:443 - returns: socket: Bad file descriptor connect:errno=9
Make sure that you aren't blocking the licensing server IP addresses: IPv4 188.8.131.52 and IPv6 2607:5300:60:2106:: Imunify360 is known to block our server IPs for some reason.