Or it may simply have not started. I would start by checking the GUID in /etc/NitroGuard/devSettings.conf matches the id in /etc/NitroGuard/cluster.conf and the GUID for the receiver component of the combined appliance from the devicecluster table of the dbserver database.
Once those match, restarting the databus service then initiating a cluster topic creation should resolve this.
I recommend raising a service request so McAfee SIEM Support can assist.
At present this cannot be done in the HTML interface, when it was last flagged it was marked as future functionality. For now, all I can suggest is to use the Flash interface.