SSL certificate error: An unknown error occurred. Please try again later

You still need to install the SSL private key and certificate to your account. See: How to install an SSL certificate

In your control panel, the certificate box is empty, but the CSR box does not. This means you used the “Generate Key/CSR” button. Please note that you don’t need to use this function if you use our free SSL certificates, and that using this function removes any private key and certificate uploaded before.