The SQL Server monitor may return the following error message when it is unable to gather SQL server performance data from the Windows agent:

Error: bad data returned from agent

Common causes of this problem include:

• An instance used in the service monitor does not exist or no instance value is required.
• The Windows agent is unable to access the SQL server performance counters on the agent.
• The Windows agent is out of date and needs to be updated to the latest version to match the SQL Server monitor functionality.