Error The State System message file processing processed one or more files that contained errors or invalid data. Review the statesys.log file for further details.

Error :The State System message file processing processed one or more files that contained errors or invalid data. Review the statesys.log file for further details.

The log file states that a specific computer's key is not in the database. Maybe the client record was aged out, or deleted manually. Thus, since there is no valid key for that client, the state system is not accepting the client's data.

What I'd do is to go to the client in question, and initiate a Discovery Data Collection Cycle, and see if that fixes the issue. I'd then go to the All Systems collection, update the collection membership, wait a minute or so, then refresh. I'd then look at the properties of this system. I'd then find the AgentName entry that says Heartbeat Discovery, and then use that same value (such as AgentName[0]) to verify the data is current - you'd use AgentTime[0] if AgentName was [0] for Heartbeat Discovery.