Make sure you have the correct file copied and not your self-signed certificate, your previous SSL, or if it is bundled as a PKCS7 or PKCS12. Or, you could have a pass-phrase that does not have alpha-numeric characters or disallowed characters. If this is the case, you will need to generate a new CSR without the disallowed characters or in the proper form. Please only use the English alphabet and numbers 0-9. For example, if the “&” symbol is included in your Organization Name, please type out “and” instead.