This is the free-text description of the current state of the FSM workflow running against this PSU. Where fsmStatus gives a coded status, this field gives the human-readable explanation of what's actually happening at this moment in that workflow, which is what an admin actually reads first when trying to understand why a PSU operation is taking longer than expected. A value here might read something like 'waiting for device to respond to configuration request', explaining the current holdup in the workflow.