The cause of this issue is an AgentGUID mismatch. The mismatch occurs when a client is forcibly removed from the environment and then reintroduced without removing the PA agent engine first. (Specifically, MA is force uninstalled and deleted from the ePolicy Orchestrator system tree, and then MA reinstalled and ePO system tree populated.) The PA agent engine retains all previously installed MA information and does not overwrite it when a new MA is installed.