On a fresh SuMa 3 installation the selected channels are not synced with the SCC automatically.
The Tomcat log shows warnings and errors:

WARN  com.redhat.rhn.manager.setup.MirrorCredentialsManager - Empty name for: SM_ENT_MGM_V
2016-06-01 13:54:15,779 [ajp-nio-] ERROR com.redhat.rhn.common.localization.LocalizationService - *** ERROR: Message with id: [task.status.gatherer] not found.*** called by com.redhat.rhn.frontend.struts.XmlMessageResources.getMessage(XmlMessageResources.java:85)
Manual sync of channels is successful, though:

spacewalk-repo-sync --channel sles11-sp3-pool-x86_64 --type yum --non-interactive
Any hint appreciated.