Installing SSL cert - screens don't match docs

Could someone help me figure out how to install a new SSL cert I just received from Comodo? I’ve been on with LiveChat, and they keep telling me I have the wrong pair, but I can’t seem to get them to explain why. They also sent me to the HSphere docs (which I already checked) which do NOT match the screens I’m seeing in my CP.

Whatever I try, I keep getting this error: Different key and certificate

I generated the CSR this morning and submitted to Comodo. I am entering the cert I received back from them.

Also, does anyone know why my CP screens differ from the docs? Are there updated docs I should be looking at?

Thanks

do you have backup of the private key generated with the CSR?

Yes, I have a backup. I tried pasting that into the form - same error.

Is it necessary to specify Apache when generating the CSR, even though this will be installed on a Windows server?

It maybe necessary to say apache when buying the cert.