Creating SSL Key Using StartSSL

I am trying to set-up a SSL certificate using Start SSL ( and my VPS server. I’m just a beginner when it comes to servers but I was hoping that I could set-up the SSL certificate in my domain’s cPanel using the SSL/TLS Manager. However, when I add the Private Key that I’ve generated using Start SSL it always says:

“The system failed to save the private key to your account.
The key could not be processed. Please make sure it is in the correct format.”

Why is it saying this? In Start SSL I’m creating the Private Key using the setting Web Server SSL/TLS Certificate and then choosing a keysize of 2048 (which is the same as that asked for in the cPanel) and I’ve tried doing it both as SHA1 and SHA2 but having no luck on either.

Is there an underlying reason for why this isn’t working that I’m just not understanding?

Any help would be greatly appreciated!