I'm trying to install an SSL in WHM so that when someone is redirected to the secure login of cPanel and WHM they don't get a warning message. Whenever I do this I get some error, either that

"Attempting to verify your certificate..... Modulus mismatch, key file does not match certificate. Please use the correct key file"

or

"Attempting to verify your certificate..... Certificate verification failed!
Verifcation Result []"

I am using a GoDaddy SSL.

I get this error no matter how I do, either by going through the "Install a SSL Certificate and Setup the Domain" or the "Manage Service SSL Certificates" option and going to "cPanel/WHM/Webmail Service"

First of all, are you sure the key and cert match? You should also check that there are no white spaces, one extra space anywhere in the key will throw it off.

first of all you need a dedicated ip to set up an SSL,
and you can install ssl completely from your WHM and no need to login in cpanel