...and how many times did you do this?
The error message is pretty clear, especially once you look at the page it points you to--you've already created five identical certificates within the past week, and there's simply no good reason for you to have done this. You'll need to wait until a week after the first one was issued to be able to issue another for that set of names. This is why the staging environment is there, so you can do your testing there, and only get certs from the production server once you've worked out all the kinks.
As a workaround, if you can add another name to the cert, it should let you issue it.