I referred to Re: error 604 before I asked my question. It is not the same
That is because your Kuler is not installed by Creative Cloud Desktop, or Kuler need to be updated, so Creative Cloud Desktop will try to reinstall it again, but encountered a 604 issue.
As some user are suffering this issue, we are still working on this. That probably your desktop unable to access some certain server, sorry for the inconvenience.