I'm getting below error from WHM. Could this mean CSR in WHM is different to what was given to SSL provider?
Error SSL install aborted due to error: Modulus mismatch, key file does not match certificate. Please use the correct key file
Jae, I'm normally a fan of people posting things to serverfault unredacted, but you've just posted an unencrypted SSL private key. I hope you understand that you can never use this private key, nor any certificate based on it, on a secure webserver. Because you've posted the private key, anyone can decrypt any traffic going to or from your server; once you put the server live, and anyone can get the corresponding certificate from it just by asking it, anyone can then undetectably impersonate your secure server.
If you're still interested in solving the underlying problem, please post your certificate and a transcript of what happens when you try to start the server - but don't think that that certificate can ever be safely used.
Edit: I'm glad you've taken the private key down, but I suspect it can still be retrieved through the change log this site keeps of edits to your post, and there may not be much you can do about that. Please, consider the key's security violated.
Now, can we see the certificate and the transcript?