On Satelllite 5, Satellite-sync fails with an identification error while trying to sync against rhn using the --iss option

Issue

On Satelllite 5, Satellite-sync fails with an identification error while trying to sync against rhn using the --iss option, producing the error messages

10:30:22 Red Hat Satellite - live synchronization
10:30:22    url: https://satellite.rhn.redhat.com
10:30:22    debug/output level: 1
10:30:23
10:30:23
ERROR: There was a problem communicating with the ISS Master.
       If the master satellite is older than v5.3, it does not have ISS capability.
       Otherwise, depending on the specific error details, please review your
       configuration, basic network connectivity, and/or name resolution, and try again.
       Error message:
Error Message:
    Please run rhn_register (or up2date                     --register on Red Hat Enterprise Linux 3 or later)
                    as root on this client
Error Class Code: 9
Error Class Info: Invalid System Credentials.
Explanation:
     An error has occurred while processing your request. If this problem
     persists please enter a bug report at bugzilla.redhat.com.
     If you choose to submit the bug report, please be sure to include
     details of what you were trying to do when this error occurred and
     details on how to reproduce this problem.