This error can occur in the Infrastructure Manager Alarm console:
[RPC Fault faultString="com.nimsoft.ui.app.common.BackendException : NimBUS error: Received status (6) on response (for sendRcv) for cmd = 'assign_to_list'" faultCode="Server.Processing" faultDetail="null"]
It is likely because something changed in your primary hub probe security.
In Infrastructure Manager, select the "Security" menu, then go to "Probe Administration". Make sure the wasp is in there and that it has "Write" or "Admin" permission.