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I'm trying to install SSL certificate provided by RapidSSL and CRT file was correctly provided to Rapid and they issues with a new SSL certificate.

I have allocated a dedicated ip address for this domain but when I try to install the certificate it comes up with below error:

Modulus mismatch, key file does not match certificate. Please use the correct key file 

What could this mean?

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the error is simple, your private key file you are using is not actually the one used to generate the CSR for your ssl certificate, you should locate the correct key file and reference that one in your apache ssl vhost

this is the basics of how ssl works and how ssl validation works. You create your key, but rather than providing it to a certificate provider to generate and sign an ssl which would be unsecure, you generate a csr which generates enough data to allow the ssl company to sign a certificate for you. therefore if you dont use this same private key with your actual ssl certificate it will fail because they dont match up to each other

where did you generate your csr for the ssl certificate? its probably likely that the key is somewhere there too

provide some more info about your system and i can advise better where to look

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I understand what you are saying but I have provided the correct CSR and this is not the first time I do this. The CSR is generated in WHM but this domain had SSL without www for the domain name so the name did not match as SSL was issued without www and the site was built with www. So we had to get another SSL which is issued with www under domain name. I heard that when you initially install SSL and cancel, it caches the old CSR. Is this correct? If so, how do we go about clearing this cache? – Passionate Developer Oct 27 '11 at 20:29
ssl/tls cert manager will allow you to delete old keys, csr's and crt's – anthonysomerset Oct 28 '11 at 6:44

Ask the folks at cpanel.

FYI, I think you meant a CSR, not a "CRT"; the former means a Certificate Signing Request, the latter is a type of computer screen.

The apache log should hold more information, in case you are inclined to look there.

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a CRT file is an ssl certificate file..... he's also provided the error already :) – anthonysomerset Oct 27 '11 at 11:10
A certificate does not have a specific filename extension; it may be PKCS[7|12] or PEM, to indicate the certificate format, or, indeed, .floobibar. – adaptr Oct 27 '11 at 11:19
i just meant in reference to this question ;) – anthonysomerset Oct 27 '11 at 12:17
I understood you ;) However, even so it makes more sense to me that he had a CSR that is to be signed by his CA. – adaptr Oct 27 '11 at 12:19

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