To check if your certificate file matches with the key, you can use the following commands.

openssl rsa -noout -modulus -in FILENAME.key
openssl req -noout -modulus -in FILENAME.csr
openssl x509 -noout -modulus -in FILENAME.cert

If you get different output, then you files do NOT match and you will need to reissue your certificate.
To make sure that you will have correct files next time, you should backup and delete old files and regenerate the new ones, by using CWP – SSL Generator.

To generate a new Certificate Files go to:
– CWP Left Menu –> Security –> SSL Generator

To install a new Certificate for your domain go to
– CWP Left Menu –> Apache Settings –> SSL Cert Manager