Today we had this strange error in WHM while attempting to install SSL certificate for a domain. Auto-fill option worked just fine and filled each field with correct data. But clicking on “Install” button kept showing the above error message. To overcome it, I have gone to WHM >> Home » SSL/TLS » Manage SSL Hosts and “Deleted” the SSL virtualhost for the domain, for which I am attempting to install new certificate. Then tried to install the certificate again and it worked just fine. I believe the error occurred due to the conflict/missing SSL certificate details configured with the old SSLvirtualhost.